The Ethereal FAQ Note: This is just an ASCII snapshot of the faq and may not be up to date. Please go to http://www.ethereal.com/faq.html for the up to date version. The version of this snapshot can be found at the end of this document. INDEX General Questions: 1.1 Where can I get help? 1.2 How much does Ethereal cost? 1.3 Can I use Ethereal commercially? 1.4 Can I use Ethereal as part of my commercial product? 1.5 What protocols are currently supported? 1.6 Are there any plans to support {your favorite protocol}? 1.7 Can Ethereal read capture files from {your favorite network analyzer}? 1.8 What devices can Ethereal use to capture packets? 1.9 How do you pronounce Ethereal? Where did the name come from? Downloading Ethereal: 2.1 I downloaded the Win32 installer, but when I try to run it, I get an error. 2.2 When I try to download the WinPcap driver and library, I can't get to the WinPcap Web site. Installing Ethereal: 3.1 I installed an Ethereal RPM, but Ethereal doesn't seem to be installed; only Tethereal is installed. Building Ethereal: 4.1 The configure script can't find pcap.h or bpf.h, but I have libpcap installed. 4.2 Why do I get the error dftest_DEPENDENCIES was already defined in condition TRUE, which implies condition HAVE_PLUGINS_TRUE when I try to build Ethereal from SVN or a SVN snapshot? 4.3 The link fails with a number of "Output line too long." messages followed by linker errors. 4.4 The link fails on Solaris because plugin_list is undefined. 4.5 The build fails on Windows because of conflicts between winsock.h and winsock2.h. Using Ethereal: 5.1 When I use Ethereal to capture packets, I see only packets to and from my machine, or I'm not seeing all the traffic I'm expecting to see from or to the machine I'm trying to monitor. 5.2 I can't see any TCP packets other than packets to and from my machine, even though another analyzer on the network sees those packets. 5.3 I'm only seeing ARP packets when I try to capture traffic. 5.4 I'm running Ethereal on Windows; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? 5.5 I'm running Ethereal on Windows; why do no network interfaces show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start"? 5.6 I'm running Ethereal on Windows; why doesn't my serial port/ADSL modem/ISDN modem show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start"? 5.7 I'm running Ethereal on a UNIX-flavored OS; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? 5.8 I'm running Ethereal on a UNIX-flavored OS; why do no network interfaces show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start"? 5.9 Can Ethereal capture on (my T1/E1 line, SS7 links, etc.)? 5.10 How do I put an interface into promiscuous mode? 5.11 I can set a display filter just fine, but capture filters don't work. 5.12 I'm entering valid capture filters, but I still get "parse error" errors. 5.13 I saved a filter and tried to use its name to filter the display, but I got an "Unexpected end of filter string" error. 5.14 Why am I seeing lots of packets with incorrect TCP checksums? 5.15 I've just installed Ethereal, and the traffic on my local LAN is boring. 5.16 When I run Ethereal on Solaris 8, it dies with a Bus Error when I start it. 5.17 When I run Ethereal, I get an error Gtk-CRITICAL **: file gtkwindow.c: line 3107 (gtk_window_resize): assertion `height > 0' failed. 5.18 When I run Tethereal with the "-x" option, it crashes with an error "** ERROR **: file print.c: line 691 (print_line): should not be reached. 5.19 When I run Ethereal on Windows NT, it dies with a Dr. Watson error, reporting an "Integer division by zero" exception, when I start it. 5.20 When I try to run Ethereal, it complains about sprint_realloc_objid being undefined. 5.21 I'm running Ethereal on Linux; why do my time stamps have only 100ms resolution, rather than 1us resolution? 5.22 I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why are the time stamps on packets wrong? 5.23 When I try to run Ethereal on Windows, it fails to run because it can't find packet.dll. 5.24 I'm running Ethereal on Windows NT 4.0/Windows 2000/Windows XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows up in the "Interface" item in the "Capture Options" dialog box. Why can no packets be sent on or received from that network while I'm trying to capture traffic on that interface? 5.25 I'm running Ethereal on Windows 95/98/Me, on a machine with more than one network adapter of the same type; Ethereal shows all of those adapters with the same name, but I can't use any of those adapters other than the first one. 5.26 I'm running Ethereal on Windows, and I'm not seeing any traffic being sent by the machine running Ethereal. 5.27 I'm trying to capture traffic but I'm not seeing any. 5.28 I have an XXX network card on my machine; if I try to capture on it, my machine crashes or resets itself. 5.29 My machine crashes or resets itself when I select "Start" from the "Capture" menu or select "Preferences" from the "Edit" menu. 5.30 Does Ethereal work on Windows Me? 5.31 Does Ethereal work on Windows XP? 5.32 Why doesn't Ethereal correctly identify RTP packets? It shows them only as UDP. 5.33 Why doesn't Ethereal show Yahoo Messenger packets in captures that contain Yahoo Messenger traffic? 5.34 Why do I get the error Gdk-ERROR **: Palettized display (256-colour) mode not supported on Windows. aborting.... when I try to run Ethereal on Windows? 5.35 When I capture on Windows in promiscuous mode, I can see packets other than those sent to or from my machine; however, those packets show up with a "Short Frame" indication, unlike packets to or from my machine. What should I do to arrange that I see those packets in their entirety? 5.36 I'm capturing packets on a machine on a VLAN; why don't the packets I'm capturing have VLAN tags? 5.37 How can I capture raw 802.11 packets, including non-data (management, beacon) packets? 5.38 How do I capture on an 802.11 device in monitor mode on Linux? 5.39 How do I capture on an 802.11 device in monitor mode on FreeBSD? 5.40 How do I capture on an 802.11 device in monitor mode on NetBSD? 5.41 I'm trying to capture 802.11 traffic on Windows; why am I not seeing any packets? 5.42 I'm trying to capture 802.11 traffic on Windows; why am I seeing packets received by the machine on which I'm capturing traffic, but not packets sent by that machine? 5.43 How can I capture packets with CRC errors? 5.44 How can I capture entire frames, including the FCS? 5.45 Why does Ethereal hang after I stop a capture? 5.46 How can I search for, or filter, packets that have a particular string anywhere in them? 5.47 How do I filter a capture to see traffic for virus XXX? General Questions Q 1.1: Where can I get help? A: Support is available on the ethereal-users mailing list. Subscription information and archives for all of Ethereal's mailing lists can be found at http://www.ethereal.com/lists Q 1.2: How much does Ethereal cost? A: Ethereal is "free software"; you can download it without paying any license fee. The version of Ethereal you download isn't a "demo" version, with limitations not present in a "full" version; it is the full version. The license under which Ethereal is issued is the GNU General Public License. See the GNU GPL FAQ for some more information. Q 1.3: Can I use Ethereal commercially? A: Yes, if, for example, you mean "I work for a commercial organization; can I use Ethereal to capture and analyze network traffic in our company's networks or in our customer's networks?" If you mean "Can I use Ethereal as part of my commercial product?", see the next entry in the FAQ. Q 1.4: Can I use Ethereal as part of my commercial product? A: As noted, Ethereal is licensed under the GNU General Public License. The GPL imposes conditions on your use of GPL'ed code in your own products; you cannot, for example, make a "derived work" from Ethereal, by making modifications to it, and then sell the resulting derived work and not allow recipients to give away the resulting work. You must also make the changes you've made to the Ethereal source available to all recipients of your modified version; those changes must also be licensed under the terms of the GPL. See the GPL FAQ for more details; in particular, note the answer to the question about modifying a GPLed program and selling it commercially, and the question about linking GPLed code with other code to make a proprietary program. You can combine a GPLed program such as Ethereal and a commercial program as long as they communicate "at arm's length", as per this item in the GPL FAQ. Q 1.5: What protocols are currently supported? A: There are currently 658 supported protocols and media, listed below. Descriptions can be found in the ethereal(1) man page. 3GPP2 A11 802.1q Virtual LAN 802.1x Authentication AAL type 2 signalling protocol - Capability set 1 (Q.2630.1) ACN AFS (4.0) Replication Server call declarations AIM Administrative AIM Advertisements AIM Buddylist Service AIM Chat Navigation AIM Chat Service AIM Directory Search AIM E-mail AIM Generic Service AIM ICQ AIM Invitation Service AIM Location AIM Messaging AIM OFT AIM Popup AIM Privacy Management Service AIM Server Side Info AIM Server Side Themes AIM Signon AIM Statistics AIM Translate AIM User Lookup ANSI A-I/F BSMAP ANSI A-I/F DTAP ANSI IS-637-A (SMS) Teleservice Layer ANSI IS-637-A (SMS) Transport Layer ANSI IS-683-A (OTA (Mobile)) ANSI IS-801 (Location Services (PLD)) ANSI Mobile Application Part AOL Instant Messenger ARCNET ASN.1 decoding ATAoverEthernet ATM ATM AAL1 ATM AAL3/4 ATM LAN Emulation ATM OAM AAL AVS WLAN Capture header AX/4000 Test Block Ad hoc On-demand Distance Vector Routing Protocol Adaptive Multi-Rate Address Resolution Protocol Aggregate Server Access Protocol Alert Standard Forum Alteon - Transparent Proxy Cache Protocol Andrew File System (AFS) Apache JServ Protocol v1.3 Apple IP-over-IEEE 1394 AppleTalk Filing Protocol AppleTalk Session Protocol AppleTalk Transaction Protocol packet Appletalk Address Resolution Protocol Application Configuration Access Protocol Art-Net Async data over ISDN (V.120) Asynchronous Layered Coding Authentication Header BACnet Virtual Link Control BEA Tuxedo BSSAP/BSAP Banyan Vines ARP Banyan Vines Echo Banyan Vines Fragmentation Protocol Banyan Vines ICP Banyan Vines IP Banyan Vines IPC Banyan Vines LLC Banyan Vines RTP Banyan Vines SPP Base Station Subsystem GPRS Protocol Basic Encoding Rules (ASN.1 X.690) Bearer Independent Call Control Bi-directional Fault Detection Control Message BitTorrent Blocks Extensible Exchange Protocol Blubster/Piolet MANOLITO Protocol Boardwalk Boot Parameters Bootstrap Protocol Border Gateway Protocol Building Automation and Control Network APDU Building Automation and Control Network NPDU CBAPhysicalDevice CCSDS CDS Clerk Server Calls Cast Client Control Protocol Certificate Management Protocol Certificate Request Message Format Check Point High Availability Protocol Checkpoint FW-1 Cisco Auto-RP Cisco Discovery Protocol Cisco Group Management Protocol Cisco HDLC Cisco Hot Standby Router Protocol Cisco ISL Cisco Interior Gateway Routing Protocol Cisco NetFlow Cisco SLARP Cisco Session Management Clearcase NFS CoSine IPNOS L2 debug output Common Industrial Protocol Common Open Policy Service Common Unix Printing System (CUPS) Browsing Protocol Compuserve GIF Configuration Test Protocol (loopback) Connectionless Lightweight Directory Access Protocol Coseventcomm Dissector Using GIOP API Cosnaming Dissector Using GIOP API Cross Point Frame Injector Cryptographic Message Syntax DCE Distributed Time Service Local Server DCE Distributed Time Service Provider DCE Name Service DCE RPC DCE Security ID Mapper DCE/RPC BOS Server DCE/RPC BUDB DCE/RPC BUTC DCE/RPC CDS Solicitation DCE/RPC Conversation Manager DCE/RPC Directory Acl Interface DCE/RPC Endpoint Mapper DCE/RPC Endpoint Mapper v4 DCE/RPC FLDB DCE/RPC FLDB UBIK TRANSFER DCE/RPC FLDB UBIKVOTE DCE/RPC ICL RPC DCE/RPC Kerberos V DCE/RPC NCS 1.5.1 Local Location Broker DCE/RPC Operations between registry server replicas DCE/RPC Prop Attr DCE/RPC RS_ACCT DCE/RPC RS_BIND DCE/RPC RS_MISC DCE/RPC RS_PROP_ACCT DCE/RPC RS_UNIX DCE/RPC Registry Password Management DCE/RPC Registry Server Attributes Schema DCE/RPC Registry server propagation interface - ACLs. DCE/RPC Registry server propagation interface - PGO items DCE/RPC Registry server propagation interface - properties and poli cies DCE/RPC Remote Management DCE/RPC Repserver Calls DCE/RPC TokenServer Calls DCE/RPC UpServer DCOM DCOM IDispatch DCOM IRemoteActivation DCOM OXID Resolver DEC Spanning Tree Protocol DFS Calls DG Gryphon Protocol DHCP Failover DHCPv6 DICOM DNS Control Program Server DOCSIS 1.1 DOCSIS Appendix C TLV's DOCSIS Baseline Privacy Key Management Attributes DOCSIS Baseline Privacy Key Management Request DOCSIS Baseline Privacy Key Management Response DOCSIS Dynamic Service Addition Acknowledge DOCSIS Dynamic Service Addition Request DOCSIS Dynamic Service Addition Response DOCSIS Dynamic Service Change Acknowledgement DOCSIS Dynamic Service Change Request DOCSIS Dynamic Service Change Response DOCSIS Dynamic Service Delete Request DOCSIS Dynamic Service Delete Response DOCSIS Initial Ranging Message DOCSIS Mac Management DOCSIS Range Request Message DOCSIS Ranging Response DOCSIS Registration Acknowledge DOCSIS Registration Requests DOCSIS Registration Responses DOCSIS Upstream Bandwidth Allocation DOCSIS Upstream Channel Change Request DOCSIS Upstream Channel Change Response DOCSIS Upstream Channel Descriptor DOCSIS Upstream Channel Descriptor Type 29 DOCSIS Vendor Specific Endodings Data Data Link SWitching Data Stream Interface Datagram Delivery Protocol Decompressed SigComp message as raw text Diameter Protocol Digital Audio Access Protocol Distance Vector Multicast Routing Protocol Distcc Distributed Compiler Distributed Checksum Clearinghouse Protocol Distributed Network Protocol 3.0 Domain Name Service Dynamic DNS Tools Protocol ENTTEC Echo Encapsulating Security Payload Endpoint Name Resolution Protocol Enhanced Interior Gateway Routing Protocol EtherNet/IP (Industrial Protocol) Etheric Ethernet Ethernet over IP Extended Security Services Extensible Authentication Protocol FC Extended Link Svc FC Fabric Configuration Server FCIP FTP Data FTServer Operations Fiber Distributed Data Interface Fibre Channel Fibre Channel Common Transport Fibre Channel Fabric Zone Server Fibre Channel Name Server Fibre Channel Protocol for SCSI Fibre Channel SW_ILS Fibre Channel Security Protocol Fibre Channel Single Byte Command File Transfer Protocol (FTP) Financial Information eXchange Protocol Frame Frame Relay GARP Multicast Registration Protocol GARP VLAN Registration Protocol GPRS Network service GPRS Tunneling Protocol GSM A-I/F BSSMAP GSM A-I/F DTAP GSM A-I/F RP GSM Mobile Application Part GSM SMS TPDU (GSM 03.40) GSM Short Message Service User Data General Inter-ORB Protocol Generic Routing Encapsulation Generic Security Service Application Program Interface Gnutella Protocol H.248 MEGACO H235-SECURITY-MESSAGES HP Extended Local-Link Control HP Remote Maintenance Protocol Hummingbird NFS Daemon HyperSCSI Hypertext Transfer Protocol ICBAAccoCallback ICBAAccoCallback2 ICBAAccoMgt ICBAAccoMgt2 ICBAAccoServer ICBAAccoServer2 ICBAAccoServerSRT ICBAAccoSync ICBABrowse ICBABrowse2 ICBAGroupError ICBAGroupErrorEvent ICBALogicalDevice ICBALogicalDevice2 ICBAPersist ICBAPersist2 ICBAPhysicalDevice ICBAPhysicalDevice2 ICBAPhysicalDevicePC ICBAPhysicalDevicePCEvent ICBARTAuto ICBARTAuto2 ICBAState ICBAStateEvent ICBASystemProperties ICBATime ICQ Protocol IEEE 802.11 Radiotap Capture header IEEE 802.11 wireless LAN IEEE 802.11 wireless LAN management frame IEEE802a OUI Extended Ethertype ILMI IP Device Control (SS7 over IP) IP Over FC IP Payload Compression IP Virtual Services Sync Daemon IPX Message IPX Routing Information Protocol IPX WAN IRemUnknown IRemUnknown2 ISDN ISDN Q.921-User Adaptation Layer ISDN User Part ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol ISO 8073 COTP Connection-Oriented Transport Protocol ISO 8327-1 OSI Session Protocol ISO 8473 CLNP ConnectionLess Network Protocol ISO 8602 CLTP ConnectionLess Transport Protocol ISO 8823 OSI Presentation Protocol ISO 9542 ESIS Routeing Information Exchange Protocol ISystemActivator ISystemActivator Resolver ITU-T E.164 number ITU-T Recommendation H.261 ITU-T Recommendation H.263 RTP Payload header (RFC2190) InMon sFlow Information Access Protocol Intel ANS probe Intelligent Platform Management Interface Inter-Access-Point Protocol Inter-Asterisk eXchange v2 InterSwitch Message Protocol Interbase Internet Cache Protocol Internet Communications Engine Protocol Internet Content Adaptation Protocol Internet Control Message Protocol Internet Control Message Protocol v6 Internet Group Management Protocol Internet Group membership Authentication Protocol Internet Message Access Protocol Internet Printing Protocol Internet Protocol Internet Protocol Version 6 Internet Relay Chat Internet Security Association and Key Management Protocol Internetwork Packet eXchange IrCOMM Protocol IrDA Link Access Protocol IrDA Link Management Protocol JPEG File Interchange Format JXTA P2P Jabber XML Messaging Java RMI Java Serialization Kerberos Kerberos Administration Kerberos v4 Kernel Lock Manager LWAP Control Message LWAPP Encapsulated Packet LWAPP Layer 3 Packet Label Distribution Protocol Laplink Layer 2 Tunneling Protocol Light Weight DNS RESolver (BIND9) Lightweight Directory Access Protocol Line Printer Daemon Protocol Line-based text data Link Access Procedure Balanced (LAPB) Link Access Procedure Balanced Ethernet (LAPBETHER) Link Access Procedure, Channel D (LAPD) Link Aggregation Control Protocol Link Management Protocol (LMP) Linux cooked-mode capture Local Management Interface LocalTalk Link Access Protocol Log Message Logical Link Control GPRS Logical-Link Control Logotype Certificate Extensions Lucent/Ascend debug output MAC Control MAP_DialoguePDU MDS Header MEGACO MIME Multipart Media Encapsulation MMS Message Encapsulation MS Kpasswd MS Proxy Protocol MSN Messenger Service MSNIP: Multicast Source Notification of Interest Protocol MTP 2 Transparent Proxy MTP 2 User Adaptation Layer MTP 3 User Adaptation Layer MTP2 Peer Adaptation Layer Media Gateway Control Protocol Media Type Media Type: message/http Message Transfer Part Level 2 Message Transfer Part Level 3 Message Transfer Part Level 3 Management Meta Analysis Tracing Engine Microsoft Directory Replication Service Microsoft Distributed File System Microsoft Distributed Link Tracking Server Service Microsoft Encrypted File System Service Microsoft Eventlog Service Microsoft Exchange MAPI Microsoft File Replication Service Microsoft File Replication Service API Microsoft Local Security Architecture Microsoft Local Security Architecture (Directory Services) Microsoft Messenger Service Microsoft Network Logon Microsoft Registry Microsoft Security Account Manager Microsoft Server Service Microsoft Service Control Microsoft Spool Subsystem Microsoft Task Scheduler Service Microsoft Telephony API Service Microsoft Windows Browser Protocol Microsoft Windows Lanman Remote API Protocol Microsoft Windows Logon Protocol Microsoft Workstation Service Mobile IP Mobile IPv6 Modbus/TCP Mount Service MultiProtocol Label Switching Header Multicast Router DISCovery protocol Multicast Source Discovery Protocol Multiprotocol Label Switching Echo MySQL Protocol NFSACL NFSAUTH NIS+ NIS+ Callback NSPI NTLM Secure Service Provider Name Binding Protocol Name Management Protocol over IPX Negative-acknowledgment Oriented Reliable Multicast NetBIOS NetBIOS Datagram Service NetBIOS Name Service NetBIOS Session Service NetBIOS over IPX NetScape Certificate Extensions NetWare Core Protocol NetWare Link Services Protocol NetWare Serialization Protocol Network Data Management Protocol Network File System Network Lock Manager Protocol Network News Transfer Protocol Network Service Over IP Network Status Monitor CallBack Protocol Network Status Monitor Protocol Network Time Protocol Nortel SONMP Novell Distributed Print System Novell Modular Authentication Service Null/Loopback OSI ISO 8571 FTAM Protocol OSI ISO/IEC 10035-1 ACSE Protocol Online Certificate Status Protocol Open Policy Service Interface Open Shortest Path First OpenBSD Encapsulating device OpenBSD Packet Filter log file OpenBSD Packet Filter log file, pre 3.4 Optimized Link State Routing Protocol PC NFS PKCS#1 PKINIT PKIX CERT File Format PKIX Qualified PKIX Time Stamp Protocol PKIX1Explitit PKIX1Implitit PKIXProxy (RFC3820) PPP Bandwidth Allocation Control Protocol PPP Bandwidth Allocation Protocol PPP CDP Control Protocol PPP Callback Control Protocol PPP Challenge Handshake Authentication Protocol PPP Compressed Datagram PPP Compression Control Protocol PPP IP Control Protocol PPP IPv6 Control Protocol PPP In HDLC-Like Framing PPP Link Control Protocol PPP MPLS Control Protocol PPP Multilink Protocol PPP Multiplexing PPP OSI Control Protocol PPP Password Authentication Protocol PPP VJ Compression PPP-over-Ethernet Discovery PPP-over-Ethernet Session PPPMux Control Protocol PROFINET DCP PROFINET IO PROFINET Real-Time Protocol Packed Encoding Rules (ASN.1 X.691) Packet Cable Lawful Intercept PacketCable Point-to-Point Protocol Point-to-Point Tunnelling Protocol Port Aggregation Protocol Portmap Post Office Protocol PostgreSQL Pragmatic General Multicast Precision Time Protocol (IEEE1588) Prism Privilege Server operations Protocol Independent Multicast Q.2931 Q.931 Q.933 Quake II Network Protocol Quake III Arena Network Protocol Quake Network Protocol QuakeWorld Network Protocol Qualified Logical Link Control RDM RFC 2250 MPEG1 RFC 2833 RTP Event RIPng RPC Browser RS Interface properties RSTAT RSYNC File Synchroniser RTcfg RX Protocol Radio Access Network Application Part Radius Protocol Raw packet data Real Time Streaming Protocol Real-Time Media Access Control Real-Time Publish-Subscribe Wire Protocol Real-Time Transport Protocol Real-time Transport Control Protocol Redundant Link Management Protocol Registry Server Attributes Manipulation Interface Registry server administration operations. Reliable UDP Remote Management Control Protocol Remote Override interface Remote Procedure Call Remote Program Load Remote Quota Remote Shell Remote Shutdown Remote Wall protocol Remote sec_login preauth interface. Resource ReserVation Protocol (RSVP) Rlogin Protocol Routing Information Protocol Routing Table Maintenance Protocol SADMIND SCSI SEBEK - Kernel Data Capture SGI Mount Service SMB (Server Message Block Protocol) SMB MailSlot Protocol SMB Pipe Protocol SNA-over-Ethernet SNMP Multiplex Protocol SPNEGO-KRB5 SPRAY SS7 SCCP-User Adaptation Layer SSCF-NNI SSCOP SSH Protocol Secure Socket Layer Sequenced Packet eXchange Serial Infrared Service Advertisement Protocol Service Location Protocol Session Announcement Protocol Session Description Protocol Session Initiation Protocol Session Initiation Protocol (SIP as raw text) Short Message Peer to Peer Short Message Relaying Service Signaling Compression Signalling Connection Control Part Signalling Connection Control Part Management Simple Mail Transfer Protocol Simple Network Management Protocol Simple Traversal of UDP Through NAT Sinec H1 Protocol Sipfrag Skinny Client Control Protocol SliMP3 Communication Protocol Socks Protocol SoulSeek Protocol Spanning Tree Protocol Spnego Stream Control Transmission Protocol Subnetwork Dependent Convergence Protocol Symantec Enterprise Firewall Synchronous Data Link Control (SDLC) Syslog message Systems Network Architecture Systems Network Architecture XID T.38 TACACS TACACS+ TDMA RTmac Discipline TEI Management Procedure, Channel D (LAPD) TPKT Tabular Data Stream Tazmen Sniffer Protocol Telnet Teredo IPv6 over UDP tunneling Time Protocol Time Synchronization Protocol Tiny Transport Protocol Token-Ring Token-Ring Media Access Control Transaction Capabilities Application Part Transmission Control Protocol Transparent Network Substrate Protocol Transport Adapter Layer Interface v1.0, RFC 3094 Trivial File Transfer Protocol UDP Encapsulation of IPsec Packets Universal Computer Protocol User Datagram Protocol V5.2-User Adaptation Layer Virtual Router Redundancy Protocol Virtual Trunking Protocol WAP Binary XML WAP Session Initiation Request Web Cache Coordination Protocol WebSphere MQ WebSphere MQ Programmable Command Formats Wellfleet Breath of Life Wellfleet Compression Wellfleet HDLC Who Windows 2000 DNS Wireless Session Protocol Wireless Transaction Protocol Wireless Transport Layer Security X Display Manager Control Protocol X.25 X.25 over TCP X.29 X.509 Authentication Framework X.509 Certificate Extensions X.509 Information Framework X.509 Selected Attribute Types X11 X711 CMIP Xyplex Yahoo Messenger Protocol Yahoo YMSG Messenger Protocol Yellow Pages Bind Yellow Pages Passwd Yellow Pages Service Yellow Pages Transfer Zebra Protocol Zone Information Protocol eDonkey Protocol giFT Internet File Transfer h225 h245 h450 iSCSI iSNS Q 1.6: Are there any plans to support {your favorite protocol}? A: Support for particular protocols is added to Ethereal as a result of people contributing that support; no formal plans for adding support for particular protocols in particular future releases exist. Q 1.7: Can Ethereal read capture files from {your favorite network analyzer}? A: Support for particular protocols is added to Ethereal as a result of people contributing that support; no formal plans for adding support for particular protocols in particular future releases exist. If a network analyzer writes out files in a format already supported by Ethereal (e.g., in libpcap format), Ethereal may already be able to read them, unless the analyzer has added its own proprietary extensions to that format. If a network analyzer writes out files in its own format, or has added proprietary extensions to another format, in order to make Ethereal read captures from that network analyzer, we would either have to have a specification for the file format, or the extensions, sufficient to give us enough information to read the parts of the file relevant to Ethereal, or would need at least one capture file in that format AND a detailed textual analysis of the packets in that capture file (showing packet time stamps, packet lengths, and the top-level packet header) in order to reverse-engineer the file format. Note that there is no guarantee that we will be able to reverse-engineer a capture file format. Q 1.8: What devices can Ethereal use to capture packets? A: Ethereal can read live data from Ethernet, Token-Ring, FDDI, serial (PPP and SLIP) (if the OS on which it's running allows Ethereal to do so), 802.11 wireless LAN (if the OS on which it's running allows Ethereal to do so), ATM connections (if the OS on which it's running allows Ethereal to do so), and the "any" device supported on Linux by recent versions of libpcap. See the list of supported capture media on various OSes for details (several items in there say "Unknown", which doesn't mean "Ethereal can't capture on them", it means "we don't know whether it can capture on them"; we expect that it will be able to capture on many of them, but we haven't tried it ourselves - if you try one of those types and it works, please send an update to ethereal-web[AT]ethereal.com ). It can also read a variety of capture file formats, including: * AG Group/WildPackets EtherPeek/TokenPeek/AiroPeek/EtherHelp/Packet Grabber captures * AIX's iptrace captures * Accellent's 5Views LAN agent output * Cinco Networks NetXRay captures * Cisco Secure Intrusion Detection System IPLog output * CoSine L2 debug output * DBS Etherwatch VMS text output * Endace Measurement Systems' ERF format captures * EyeSDN USB S0 traces * HP-UX nettl captures * ISDN4BSD project i4btrace captures * Linux Bluez Bluetooth stack hcidump -w traces * Lucent/Ascend router debug output * Microsoft Network Monitor captures * Network Associates Windows-based Sniffer captures * Network General/Network Associates DOS-based Sniffer (compressed or uncompressed) captures * Network Instruments Observer version 9 captures * Novell LANalyzer captures * RADCOM's WAN/LAN analyzer captures * Shomiti/Finisar Surveyor captures * Toshiba's ISDN routers dump output * VMS TCPIPtrace/TCPtrace/UCX$TRACE output * Visual Networks' Visual UpTime traffic capture * libpcap, tcpdump and various other tools using tcpdump's capture format * snoop and atmsnoop output so that it can read traces from various network types, as captured by other applications or equipment, even if it cannot itself capture on those network types. Q 1.9: How do you pronounce Ethereal? Where did the name come from? A: The English pronunciation can be found in Merriam-Webster's online dictionary at http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=ethereal. According to the book "Computer Networks" by Andrew Tannenbaum, Ethernet was named after the "luminiferous ether" which was once thought to carry electromagnetic radiation. Taking that into consideration, Ethereal seemed like an appropriate name for something that started out as an Ethernet analyzer. Downloading Ethereal Q 2.1: I downloaded the Win32 installer, but when I try to run it, I get an error. A: The program you used to download it may have downloaded it incorrectly. Web browsers sometimes may do this. Try downloading it with, for example: * Wget, for which Windows binaries are available on the SunSITE FTP server at sunsite.tk or Heiko Herold's windows wget spot - wGetGUI offers a GUI interface that uses wget; * WS_FTP from Ipswitch, * the ftp command that comes with Windows. If you use the ftp command, make sure you do the transfer in binary mode rather than ASCII mode, by using the binary command before transferring the file. Q 2.2: When I try to download the WinPcap driver and library, I can't get to the WinPcap Web site. A: As is the case with all Web sites, that site won't necessarily always be accessible; the server may be down due to a problem or down for maintenance, or there may be a networking problem between you and the server. You should try again later, or try the local mirror or the Wiretapped.net mirror. Installing Ethereal Q 3.1: I installed an Ethereal RPM, but Ethereal doesn't seem to be installed; only Tethereal is installed. A: Older versions of the Red Hat RPMs for Ethereal put only the non-GUI components into the ethereal RPM, the fact that Ethereal is a GUI program nonwithstanding; newer versions make it a bit clearer by giving that RPM a name starting with ethereal-base. In those older versions, there's a separate ethereal-gnome RPM that includes GUI components such as Ethereal itself, the fact that Ethereal doesn't use GNOME nonwithstanding; newer versions make it a bit clearer by giving that RPM a name starting with ethereal-gtk+. Find the ethereal-gnome or ethereal-gtk+ RPM, and install that also. Building Ethereal Q 4.1: The configure script can't find pcap.h or bpf.h, but I have libpcap installed. A: Are you sure pcap.h and bpf.h are installed? The official distribution of libpcap only installs the libpcap.a library file when "make install" is run. To install pcap.h and bpf.h, you must run "make install-incl". If you're running Debian or Redhat, make sure you have the "libpcap-dev" or "libpcap-devel" packages installed. It's also possible that pcap.h and bpf.h have been installed in a strange location. If this is the case, you may have to tweak aclocal.m4. Q 4.2: Why do I get the error dftest_DEPENDENCIES was already defined in condition TRUE, which implies condition HAVE_PLUGINS_TRUE when I try to build Ethereal from SVN or a SVN snapshot? A: You probably have automake 1.5 installed on your machine (the command automake --version will report the version of automake on your machine). There is a bug in that version of automake that causes this problem; upgrade to a later version of automake (1.6 or later). Q 4.3: The link fails with a number of "Output line too long." messages followed by linker errors. A: The version of the sed command on your system is incapable of handling very long lines. On Solaris, for example, /usr/bin/sed has a line length limit too low to allow libtool to work; /usr/xpg4/bin/sed can handle it, as can GNU sed if you have it installed. On Solaris, changing your command search path to search /usr/xpg4/bin before /usr/bin should make the problem go away; on any platform on which you have this problem, installing GNU sed and changing your command path to search the directory in which it is installed before searching the directory with the version of sed that came with the OS should make the problem go away. Q 4.4: The link fails on Solaris because plugin_list is undefined. A: This appears to be due to a problem with some versions of the GTK+ and GLib packages from www.sunfreeware.org; un-install those packages, and try getting the 1.2.10 versions from that site, or the versions from The Written Word, or the versions from Sun's GNOME distribution, or the versions from the supplemental software CD that comes with the Solaris media kit, or build them from source from the GTK Web site. Then re-run the configuration script, and try rebuilding Ethereal. (If you get the 1.2.10 versions from www.sunfreeware.org, and the problem persists, un-install them and try installing one of the other versions mentioned.) Q 4.5: The build fails on Windows because of conflicts between winsock.h and winsock2.h. A: As of Ethereal 0.9.5, you must install WinPcap 2.3 or later, and the corresponding version of the developer's pack, in order to be able to compile Ethereal; it will not compile with older versions of the developer's pack. The symptoms of this failure are conflicts between definitions in winsock.h and in winsock2.h; Ethereal uses winsock2.h, but pre-2.3 versions of the WinPcap developer's packet use winsock.h. (2.3 uses winsock2.h, so if Ethereal were to use winsock.h, it would not be able to build with current versions of the WinPcap developer's pack.) Note that the installed version of the developer's pack should be the same version as the version of WinPcap you have installed. Using Ethereal Q 5.1: When I use Ethereal to capture packets, I see only packets to and from my machine, or I'm not seeing all the traffic I'm expecting to see from or to the machine I'm trying to monitor. A: This might be because the interface on which you're capturing is plugged into an Ethernet or Token Ring switch; on a switched network, unicast traffic between two ports will not necessarily appear on other ports - only broadcast and multicast traffic will be sent to all ports. Note that even if your machine is plugged into a hub, the "hub" may be a switched hub, in which case you're still on a switched network. Note also that on the Linksys Web site, they say that their auto-sensing hubs "broadcast the 10Mb packets to the port that operate at 10Mb only and broadcast the 100Mb packets to the ports that operate at 100Mb only", which would indicate that if you sniff on a 10Mb port, you will not see traffic coming sent to a 100Mb port, and vice versa. This problem has also been reported for Netgear dual-speed hubs, and may exist for other "auto-sensing" or "dual-speed" hubs. Some switches have the ability to replicate all traffic on all ports to a single port so that you can plug your analyzer into that single port to sniff all traffic. You would have to check the documentation for the switch to see if this is possible and, if so, to see how to do this. See the switch reference page on the Ethereal Wiki for information on some switches. (Note that it's a Wiki, so you can update or fix that information, or add additional information on those switches or information on new switches, yourself.) Note also that many firewall/NAT boxes have a switch built into them; this includes many of the "cable/DSL router" boxes. If you have a box of that sort, that has a switch with some number of Ethernet ports into which you plug machines on your network, and another Ethernet port used to connect to a cable or DSL modem, you can, at least, sniff traffic between the machines on your network and the Internet by plugging the Ethernet port on the router going to the modem, the Ethernet port on the modem, and the machine on which you're running Ethereal into a hub (make sure it's not a switching hub, and that, if it's a dual-speed hub, all three of those ports are running at the same speed. If your machine is not plugged into a switched network or a dual-speed hub, or it is plugged into a switched network but the port is set up to have all traffic replicated to it, the problem might be that the network interface on which you're capturing doesn't support "promiscuous" mode, or because your OS can't put the interface into promiscuous mode. Normally, network interfaces supply to the host only: * packets sent to one of that host's link-layer addresses; * broadcast packets; * multicast packets sent to a multicast address that the host has configured the interface to accept. Most network interfaces can also be put in "promiscuous" mode, in which they supply to the host all network packets they see. Ethereal will try to put the interface on which it's capturing into promiscuous mode unless the "Capture packets in promiscuous mode" option is turned off in the "Capture Options" dialog box, and Tethereal will try to put the interface on which it's capturing into promiscuous mode unless the -p option was specified. However, some network interfaces don't support promiscuous mode, and some OSes might not allow interfaces to be put into promiscuous mode. If the interface is not running in promiscuous mode, it won't see any traffic that isn't intended to be seen by your machine. It will see broadcast packets, and multicast packets sent to a multicast MAC address the interface is set up to receive. You should ask the vendor of your network interface whether it supports promiscuous mode. If it does, you should ask whoever supplied the driver for the interface (the vendor, or the supplier of the OS you're running on your machine) whether it supports promiscuous mode with that network interface. In the case of token ring interfaces, the drivers for some of them, on Windows, may require you to enable promiscuous mode in order to capture in promiscuous mode. See the Ethereal Wiki item on Token Ring capturing for details. In the case of wireless LAN interfaces, it appears that, when those interfaces are promiscuously sniffing, they're running in a significantly different mode from the mode that they run in when they're just acting as network interfaces (to the extent that it would be a significant effor for those drivers to support for promiscuously sniffing and acting as regular network interfaces at the same time), so it may be that Windows drivers for those interfaces don't support promiscuous mode. Q 5.2: I can't see any TCP packets other than packets to and from my machine, even though another analyzer on the network sees those packets. A: You're probably not seeing any packets other than unicast packets to or from your machine, and broadcast and multicast packets; a switch will normally send to a port only unicast traffic sent to the MAC address for the interface on that port, and broadcast and multicast traffic - it won't send to that port unicast traffic sent to a MAC address for some other interface - and a network interface not in promiscuous mode will receive only unicast traffic sent to the MAC address for that interface, broadcast traffic, and multicast traffic sent to a multicast MAC address the interface is set up to receive. TCP doesn't use broadcast or multicast, so you will only see your own TCP traffic, but UDP services may use broadcast or multicast so you'll see some UDP traffic - however, this is not a problem with TCP traffic, it's a problem with unicast traffic, as you also won't see all UDP traffic between other machines. I.e., this is probably the same question as this earlier one; see the response to that question. Q 5.3: I'm only seeing ARP packets when I try to capture traffic. A: You're probably on a switched network, and running Ethereal on a machine that's not sending traffic to the switch and not being sent any traffic from other machines on the switch. ARP packets are often broadcast packets, which are sent to all switch ports. I.e., this is probably the same question as this earlier one; see the response to that question. Q 5.4: I'm running Ethereal on Windows; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? A: If you are running Ethereal on Windows NT 4.0, Windows 2000, Windows XP, or Windows Server 2003, and this is the first time you have run a WinPcap-based program (such as Ethereal, or Tethereal, or WinDump, or Analyzer, or...) since the machine was rebooted, you need to run that program from an account with administrator privileges; once you have run such a program, you will not need administrator privileges to run any such programs until you reboot. If you are running on Windows 95/98/Me, or if you are running on Windows NT 4.0/Windows 2000/Windows XP/Windows Server 2003 and have administrator privileges or a WinPcap-based program has been run with those privileges since the machine rebooted, then note that Ethereal relies on the WinPcap library, on the WinPcap device driver, and on the facilities that come with the OS on which it's running in order to do captures. Therefore, if the OS, the WinPcap library, or the WinPcap driver don't support capturing on a particular network interface device, Ethereal won't be able to capture on that device. Note that: 1. 2.02 and earlier versions of the WinPcap driver and library that Ethereal uses for packet capture didn't support Token Ring interfaces; versions 2.1 and later support Token Ring, and the current version of Ethereal works with (and, in fact, requires) WinPcap 2.1 or later. If you are having problems capturing on Token Ring interfaces, and you have WinPcap 2.02 or an earlier version of WinPcap installed, you should uninstall WinPcap, download and install the current version of WinPcap, and then install the latest version of Ethereal. 2. On Windows 95, 98, or Me, sometimes more than one interface will be given the same name; if that is the case, you will only be able to capture on one of those interfaces - it's not clear to which one the name, when used in a WinPcap-based application, will refer. For example, if you have a PPP serial interface and a VPN interface, they might show up with the same name, for example "ppp-mac", and if you try to capture on "ppp-mac", it might not capture on the interface you're currently using. In that case, you might, for example, have to remove the VPN interface from the system in order to capture on the PPP serial interface. 3. WinPcap 2.3 has problems supporting PPP WAN interfaces on Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003, and, to avoid those problems, support for PPP WAN interfaces on those versions of Windows has been disabled in WinPcap 3.0. Regular dial-up lines, ISDN lines, ADSL connections using PPPoE or PPPoA, and various other lines such as T1/E1 lines are all PPP interfaces, so those interfaces might not show up on the list of interfaces in the "Capture Options" dialog on those OSes. On Windows 2000 and later, installing the beta version of WinPcap 3.1 might help, although, as it's a beta version, that might cause some other problems that don't occur with older versions of WinPcap; you should report those problems to the WinPcap developers, so that they can try to fix those problems before the final version of WinPcap 3.1 is released. WinPcap 3.1 will not support PPP captures on Windows NT 4.0. See the Ethereal Wiki item on PPP capturing for details. 4. WinPcap prior to 3.0 does not support multiprocessor machines (note that machines with a single multi-threaded processor, such as Intel's new multi-threaded x86 processors, are multiprocessor machines as far as the OS and WinPcap are concerned), and recent 2.x versions of WinPcap refuse to operate if they detect that they're running on a multiprocessor machine, which means that they may not show any network interfaces. You will need to use WinPcap 3.0 to capture on a multiprocessor machine. If an interface doesn't show up in the list of interfaces in the "Interface:" field, and you know the name of the interface, try entering that name in the "Interface:" field and capturing on that device. If the attempt to capture on it succeeds, the interface is somehow not being reported by the mechanism Ethereal uses to get a list of interfaces. Try listing the interfaces with WinDump; see the WinDump Web site or the local mirror of the WinDump Web site for information on using WinDump. You would run WinDump with the -D flag; if it lists the interface, please report this to ethereal-dev@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system; * the type of network device you're using; * the output of WinDump. If WinDump does not list the interface, this is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the WinPcap library and/or the WinPcap device driver; so first check the WinPcap FAQ, the local mirror of that FAQ, or the Wiretapped.net mirror of that FAQ, to see if your problem is mentioned there. If not, then see the WinPcap support page (or the local mirror of that page) - check the "Submitting bugs" section. If you are having trouble capturing on a particular network interface, first try capturing on that device with WinDump; see the WinDump Web site or the local mirror of the WinDump Web site for information on using WinDump. If you can capture on the interface with WinDump, send mail to ethereal-users@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system; * the type of network device you're using; * the error message you get from Ethereal. If you cannot capture on the interface with WinDump, this is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the WinPcap library and/or the WinPcap device driver; so first check the WinPcap FAQ, the local mirror of that FAQ, or the Wiretapped.net mirror of that FAQ, to see if your problem is mentioned there. If not, then see the WinPcap support page (or the local mirror of that page) - check the "Submitting bugs" section. You may also want to ask the ethereal-users@ethereal.com and the winpcap-users@winpcap.polito.it mailing lists to see if anybody happens to know about the problem and know a workaround or fix for the problem. (Note that you will have to subscribe to that list in order to be allowed to mail to it; see the WinPcap support page, or the local mirror of that page, for information on the mailing list.) In your mail, please give full details of the problem, as described above, and also indicate that the problem occurs with WinDump, not just with Ethereal. Q 5.5: I'm running Ethereal on Windows; why do no network interfaces show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start"? A: This is really the same question as the previous one; see the response to that question. Q 5.6: I'm running Ethereal on Windows; why doesn't my serial port/ADSL modem/ISDN modem show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start"? A: Internet access on those devices is often done with the Point-to-Point (PPP) protocol; WinPcap 2.3 has problems supporting PPP WAN interfaces on Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003, and, to avoid those problems, support for PPP WAN interfaces on those versions of Windows has been disabled in WinPcap 3.0. On Windows 2000 and later, installing the beta version of WinPcap 3.1 might help, although, as it's a beta version, that might cause some other problems that don't occur with older versions of WinPcap; you should report those problems to the WinPcap developers, so that they can try to fix those problems before the final version of WinPcap 3.1 is released. WinPcap 3.1 will not support PPP captures on Windows NT 4.0. See the Ethereal Wiki item on PPP capturing for details. Q 5.7: I'm running Ethereal on a UNIX-flavored OS; why does some network interface on my machine not show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start", and/or why does Ethereal give me an error if I try to capture on that interface? A: You may need to run Ethereal from an account with sufficient privileges to capture packets, such as the super-user account, or may need to give your account sufficient privileges to capture packets. Only those interfaces that Ethereal can open for capturing show up in that list; if you don't have sufficient privileges to capture on any interfaces, no interfaces will show up in the list. See the Ethereal Wiki item on capture privileges for details on how to give a particular account or account group capture privileges on platforms where that can be done. If you are running Ethereal from an account with sufficient privileges, then note that Ethereal relies on the libpcap library, and on the facilities that come with the OS on which it's running in order to do captures. On some OSes, those facilities aren't present by default; see the Ethereal Wiki item on adding capture support for details. And, even if you're running with an account that has sufficient privileges to capture, and capture support is present in your OS, if the OS or the libpcap library don't support capturing on a particular network interface device or particular types of devices, Ethereal won't be able to capture on that device. On Solaris, note that libpcap 0.6.2 and earlier didn't support Token Ring interfaces; the current version, 0.7.2, does support Token Ring, and the current version of Ethereal works with libcap 0.7.2 and later. If an interface doesn't show up in the list of interfaces in the "Interface:" field, and you know the name of the interface, try entering that name in the "Interface:" field and capturing on that device. If the attempt to capture on it succeeds, the interface is somehow not being reported by the mechanism Ethereal uses to get a list of interfaces; please report this to ethereal-dev@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system (for Linux, give both the version number of the kernel and the name and version number of the distribution you're using); * the type of network device you're using. If you are having trouble capturing on a particular network interface, and you've made sure that (on platforms that require it) you've arranged that packet capture support is present, as per the above, first try capturing on that device with tcpdump. If you can capture on the interface with tcpdump, send mail to ethereal-users@ethereal.com giving full details of the problem, including * the operating system you're using, and the version of that operating system (for Linux, give both the version number of the kernel and the name and version number of the distribution you're using); * the type of network device you're using; * the error message you get from Ethereal. If you cannot capture on the interface with tcpdump, this is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the libpcap library; so you should report the problem to the company or organization that produces the OS (in the case of a Linux distribution, report the problem to whoever produces the distribution). You may also want to ask the ethereal-users@ethereal.com and the tcpdump-workers@tcpdump.org mailing lists to see if anybody happens to know about the problem and know a workaround or fix for the problem. In your mail, please give full details of the problem, as described above, and also indicate that the problem occurs with tcpdump not just with Ethereal. Q 5.8: I'm running Ethereal on a UNIX-flavored OS; why do no network interfaces show up in the list of interfaces in the "Interface:" field in the dialog box popped up by "Capture->Start"? A: This is really the same question as the previous one; see the response to that question. Q 5.9: Can Ethereal capture on (my T1/E1 line, SS7 links, etc.)? A: Ethereal can only capture on devices supported by libpcap/WinPcap. On most OSes, only devices that can act as network interfaces of the type that support IP are supported as capture devices for libpcap/WinPcap, although the device doesn't necessarily have to be running as an IP interface in order to support traffic capture. On Linux and FreeBSD, libpcap 0.8 and later support the API for Endace Measurement Systems' DAG cards, so that a system with one of those cards, and its driver and libraries, installed can capture traffic with those cards with libpcap-based applications. You would either have to have a version of Ethereal built with that version of libpcap, or a dynamically-linked version of Ethereal and a shared libpcap library with DAG support, in order to do so with Ethereal. You should ask Endace whether that could be used to capture traffic on, for example, your T1/E1 link. There is currently no hardware to support capturing on SS7 links with libpcap. (Note that the fact that Ethereal includes dissectors for many SS7 protocols doesn't imply that it can capture traffic from SS7 links; those protocols can be run over Internet protocols.) Q 5.10: How do I put an interface into promiscuous mode? A: By not disabling promiscuous mode when running Ethereal or Tethereal. Note, however, that: * the form of promiscuous mode that libpcap (the library that programs such as tcpdump, Ethereal, etc. use to do packet capture) turns on will not necessarily be shown if you run ifconfig on the interface on a UNIX system; * some network interfaces might not support promiscuous mode, and some drivers might not allow promiscuous mode to be turned on - see this earlier question for more information on that; * the fact that you're not seeing any traffic, or are only seeing broadcast traffic, or aren't seeing any non-broadcast traffic other than traffic to or from the machine running Ethereal, does not mean that promiscuous mode isn't on - see this earlier question for more information on that. I.e., this is probably the same question as this earlier one; see the response to that question. Q 5.11: I can set a display filter just fine, but capture filters don't work. A: Capture filters currently use a different syntax than display filters. Here's the corresponding section from the ethereal(1) man page: "Display filters in Ethereal are very powerful; more fields are filterable in Ethereal than in other protocol analyzers, and the syntax you can use to create your filters is richer. As Ethereal progresses, expect more and more protocol fields to be allowed in display filters. Packet capturing is performed with the pcap library. The capture filter syntax follows the rules of the pcap library. This syntax is different from the display filter syntax." The capture filter syntax used by libpcap can be found in the tcpdump(8) man page. Q 5.12: I'm entering valid capture filters, but I still get "parse error" errors. A: There is a bug in some versions of libpcap/WinPcap that cause it to report parse errors even for valid expressions if a previous filter expression was invalid and got a parse error. Try exiting and restarting Ethereal; if you are using a version of libpcap/WinPcap with this bug, this will "erase" its memory of the previous parse error. If the capture filter that got the "parse error" now works, the earlier error with that filter was probably due to this bug. The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of libpcap have this bug, but 0.6[.x] and later versions don't. Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of libpcap, and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and doesn't have this bug. If you are running Ethereal on a UNIX-flavored platform, run "ethereal -v", or select "About Ethereal..." from the "Help" menu in Ethereal, to see what version of libpcap it's using. If it's not 0.6 or later, you will need either to upgrade your OS to get a later version of libpcap, or will need to build and install a later version of libpcap from the tcpdump.org Web site and then recompile Ethereal from source with that later version of libpcap. If you are running Ethereal on Windows with a pre-2.3 version of WinPcap, you will need to un-install WinPcap and then download and install WinPcap 2.3. Q 5.13: I saved a filter and tried to use its name to filter the display, but I got an "Unexpected end of filter string" error. A: You cannot use the name of a saved display filter as a filter. To filter the display, you can enter a display filter expression - not the name of a saved display filter - in the "Filter:" box at the bottom of the display, and type the key or press the "Apply" button (that does not require you to have a saved filter), or, if you want to use a saved filter, you can press the "Filter:" button, select the filter in the dialog box that pops up, and press the "OK" button. Q 5.14: Why am I seeing lots of packets with incorrect TCP checksums? A: If the packets that have incorrect TCP checksums are all being sent by the machine on which Ethereal is running, this is probably because the network interface on which you're capturing does TCP checksum offloading. That means that the TCP checksum is added to the packet by the network interface, not by the OS's TCP/IP stack; when capturing on an interface, packets being sent by the host on which you're capturing are directly handed to the capture interface by the OS, which means that they are handed to the capture interface without a TCP checksum being added to them. The only way to prevent this from happening would be to disable TCP checksum offloading, but 1. that might not even be possible on some OSes; 2. that could reduce networking performance significantly. However, you can disable the check that Ethereal does of the TCP checksum, so that it won't report any packets as having TCP checksum errors, and so that it won't refuse to do TCP reassembly due to a packet having an incorrect TCP checksum. That can be set as an Ethereal preference by selecting "Preferences" from the "Edit" menu, opening up the "Protocols" list in the left-hand pane of the "Preferences" dialog box, selecting "TCP", from that list, turning off the "Check the validity of the TCP checksum when possible" option, clicking "Save" if you want to save that setting in your preference file, and clicking "OK". It can also be set on the Ethereal or Tethereal command line with a -o tcp.check_checksum:false command-line flag, or manually set in your preferences file by adding a tcp.check_checksum:false line. Q 5.15: I've just installed Ethereal, and the traffic on my local LAN is boring. A: We have a collection of strange and exotic sample capture files at http://wiki.ethereal.com/SampleCaptures Q 5.16: When I run Ethereal on Solaris 8, it dies with a Bus Error when I start it. A: Some versions of the GTK+ library from www.sunfreeware.org appear to be buggy, causing Ethereal to drop core with a Bus Error. Un-install those packages, and try getting the 1.2.10 version from that site, or the version from The Written Word, or the version from Sun's GNOME distribution, or the version from the supplemental software CD that comes with the Solaris media kit, or build it from source from the GTK Web site. Update the GLib library to the 1.2.10 version, from the same source, as well. (If you get the 1.2.10 versions from www.sunfreeware.org, and the problem persists, un-install them and try installing one of the other versions mentioned.) Similar problems may exist with older versions of GTK+ for earlier versions of Solaris. Q 5.17: When I run Ethereal, I get an error Gtk-CRITICAL **: file gtkwindow.c: line 3107 (gtk_window_resize): assertion `height > 0' failed. A: This is a bug in Ethereal 0.10.5 and 0.10.5a, which is fixed in Ethereal 0.10.6 and later releases. Q 5.18: When I run Tethereal with the "-x" option, it crashes with an error "** ERROR **: file print.c: line 691 (print_line): should not be reached. A: This is a bug in Ethereal 0.10.0a, which is fixed in 0.10.1 and later releases. To work around the bug, don't use "-x" unless you're also using "-V"; note that "-V" produces a full dissection of each packet, so you might not want to use it. Q 5.19: When I run Ethereal on Windows NT, it dies with a Dr. Watson error, reporting an "Integer division by zero" exception, when I start it. A: In at least some case, this appears to be due to using the default VGA driver; if that's not the correct driver for your video card, try running the correct driver for your video card. Q 5.20: When I try to run Ethereal, it complains about sprint_realloc_objid being undefined. A: Ethereal can only be linked with version 4.2.2 or later of UCD SNMP. Your version of Ethereal was dynamically linked with such a version of UCD SNMP; however, you have an older version of UCD SNMP installed, which means that when Ethereal is run, it tries to link to the older version, and fails. You will have to replace that version of UCD SNMP with version 4.2.2 or a later version. Q 5.21: I'm running Ethereal on Linux; why do my time stamps have only 100ms resolution, rather than 1us resolution? A: Ethereal gets time stamps from libpcap/WinPcap, and libpcap/WinPcap get them from the OS kernel, so Ethereal - and any other program using libpcap, such as tcpdump - is at the mercy of the time stamping code in the OS for time stamps. At least on x86-based machines, Linux can get high-resolution time stamps on newer processors with the Time Stamp Counter (TSC) register; for example, Intel x86 processors, starting with the Pentium Pro, and including all x86 processors since then, have had a TSC, and other vendors probably added the TSC at some point to their families of x86 processors. The Linux kernel must be configured with the CONFIG_X86_TSC option enabled in order to use the TSC. Make sure this option is enabled in your kernel. In addition, some Linux distributions may have bugs in their versions of the kernel that cause packets not to be given high-resolution time stamps even if the TSC is enabled. See, for example, bug 61111 for Red Hat Linux 7.2. If your distribution has a bug such as this, you may have to run a standard kernel from kernel.org in order to get high-resolution time stamps. Q 5.22: I'm capturing packets on {Windows 95, Windows 98, Windows Me}; why are the time stamps on packets wrong? A: This is due to a bug in WinPcap. The bug should be fixed in WinPcap 3.0. Q 5.23: When I try to run Ethereal on Windows, it fails to run because it can't find packet.dll. A: In older versions of Ethereal, there were two binary distributions available for Windows, one that supported capturing packets, and one that didn't. The version that supported capturing packets required that you install the WinPcap driver; if you didn't install it, it would fail to run because it couldn't find packet.dll. The current version of Ethereal has only one binary distribution for Windows; that version will check whether WinPcap is installed and, if it's not, will disable support for packet capture. The WinPcap driver and libraries can be downloaded from the WinPcap Web site, the local mirror of the WinPcap Web site, or the Wiretapped.net mirror of the WinPcap site. Q 5.24: I'm running Ethereal on Windows NT 4.0/Windows 2000/Windows XP/Windows Server 2003; my machine has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows up in the "Interface" item in the "Capture Options" dialog box. Why can no packets be sent on or received from that network while I'm trying to capture traffic on that interface? A: Some versions of WinPcap have problems with PPP WAN interfaces on Windows NT 4.0, Windows 2000, Windows XP, and Windows Server 2003; one symptom that may be seen is that attempts to capture in promiscuous mode on the interface cause the interface to be incapable of sending or receiving packets. You can disable promiscuous mode using the -p command-line flag or the item in the "Capture Preferences" dialog box, but this may mean that outgoing packets, or incoming packets, won't be seen in the capture. On Windows 2000 and later, installing the beta version of WinPcap 3.1 might help, although, as it's a beta version, that might cause some other problems that don't occur with older versions of WinPcap; you should report those problems to the WinPcap developers, so that they can try to fix those problems before the final version of WinPcap 3.1 is released. WinPcap 3.1 will not support PPP captures on Windows NT 4.0. See the Ethereal Wiki item on PPP capturing for details. Q 5.25: I'm running Ethereal on Windows 95/98/Me, on a machine with more than one network adapter of the same type; Ethereal shows all of those adapters with the same name, but I can't use any of those adapters other than the first one. A: Unfortunately, Windows 95/98/Me gives the same name to multiple instances of the type of same network adapter. Therefore, WinPcap cannot distinguish between them, so a WinPcap-based application can capture only on the first such interface; Ethereal is a libpcap/WinPcap-based application. Q 5.26: I'm running Ethereal on Windows, and I'm not seeing any traffic being sent by the machine running Ethereal. A: If you are running some form of VPN client software, it might be causing this problem; people have seen this problem when they have Check Point's VPN software installed on their machine. If that's the cause of the problem, you will have to remove the VPN software in order to have Ethereal (or any other application using WinPcap) see outgoing packets; unfortunately, neither we nor the WinPcap developers know any way to make WinPcap and the VPN software work well together. Also, some drivers for Windows (especially some wireless network interface drivers) apparently do not, when running in promiscuous mode, arrange that outgoing packets are delivered to the software that requested that the interface run promiscuously; try turning promiscuous mode off. Q 5.27: I'm trying to capture traffic but I'm not seeing any. A: Is the machine running Ethereal sending out any traffic on the network interface on which you're capturing, or receiving any traffic on that network, or is there any broadcast traffic on the network or multicast traffic to a multicast group to which the machine running Ethereal belongs? If not, this may just be a problem with promiscuous sniffing, either due to running on a switched network or a dual-speed hub, or due to problems with the interface not supporting promiscuous mode; see the response to this earlier question. Otherwise, on Windows, see the response to this question and, on a UNIX-flavored OS, see the response to this question. Q 5.28: I have an XXX network card on my machine; if I try to capture on it, my machine crashes or resets itself. A: This is almost certainly a problem with one or more of: * the operating system you're using; * the device driver for the interface you're using; * the libpcap/WinPcap library and, if this is Windows, the WinPcap device driver; so: * if you are using Windows, see the WinPcap support page (or the local mirror of that page) - check the "Submitting bugs" section; * if you are using some Linux distribution, some version of BSD, or some other UNIX-flavored OS, you should report the problem to the company or organization that produces the OS (in the case of a Linux distribution, report the problem to whoever produces the distribution). Q 5.29: My machine crashes or resets itself when I select "Start" from the "Capture" menu or select "Preferences" from the "Edit" menu. A: Both of those operations cause Ethereal to try to build a list of the interfaces that it can open; it does so by getting a list of interfaces and trying to open them. There is probably an OS, driver, or, for Windows, WinPcap bug that causes the system to crash when this happens; see the previous question. Q 5.30: Does Ethereal work on Windows Me? A: Yes, but if you want to capture packets, you will need to install the latest version of WinPcap, as 2.02 and earlier versions of WinPcap didn't support Windows Me. You should also install the latest version of Ethereal as well. Q 5.31: Does Ethereal work on Windows XP? A: Yes, but if you want to capture packets, you will need to install the latest version of WinPcap, as 2.2 and earlier versions of WinPcap didn't support Windows XP. Q 5.32: Why doesn't Ethereal correctly identify RTP packets? It shows them only as UDP. A: Ethereal can identify a UDP datagram as containing a packet of a particular protocol running atop UDP only if 1. The protocol in question has a particular standard port number, and the UDP source or destination port number is that port 2. Packets of that protocol can be identified by looking for a "signature" of some type in the packet - i.e., some data that, if Ethereal finds it in some particular part of a packet, means that the packet is almost certainly a packet of that type. 3. Some other traffic earlier in the capture indicated that, for example, UDP traffic between two particular addresses and ports will be RTP traffic. RTP doesn't have a standard port number, so 1) doesn't work; it doesn't, as far as I know, have any "signature", so 2) doesn't work. That leaves 3). If there's RTSP traffic that sets up an RTP session, then, at least in some cases, the RTSP dissector will set things up so that subsequent RTP traffic will be identified. Currently, that's the only place we do that; there may be other places. However, there will always be places where Ethereal is simply incapable of deducing that a given UDP flow is RTP; a mechanism would be needed to allow the user to specify that a given conversation should be treated as RTP. As of Ethereal 0.8.16, such a mechanism exists; if you select a UDP or TCP packet, the right mouse button menu will have a "Decode As..." menu item, which will pop up a dialog box letting you specify that the source port, the destination port, or both the source and destination ports of the packet should be dissected as some particular protocol. Q 5.33: Why doesn't Ethereal show Yahoo Messenger packets in captures that contain Yahoo Messenger traffic? A: Ethereal only recognizes as Yahoo Messenger traffic packets to or from TCP port 3050 that begin with "YPNS", "YHOO", or "YMSG". TCP segments that start with the middle of a Yahoo Messenger packet that takes more than one TCP segment will not be recognized as Yahoo Messenger packets (even if the TCP segment also contains the beginning of another Yahoo Messenger packet). Q 5.34: Why do I get the error Gdk-ERROR **: Palettized display (256-colour) mode not supported on Windows. aborting.... when I try to run Ethereal on Windows? A: Ethereal is built using the GTK+ toolkit, which supports most UNIX-flavored OSes, and also supports Windows. Windows versions of Ethereal before 0.9.14 were built with an older version of that toolkit, which didn't support 256-color mode on Windows - it required HiColor (16-bit colors) or more. Windows versions of Ethereal 0.9.14 and later are built with a version of that toolkit that supports 256-color mode; upgrade to the current version of Ethereal if you want to run on a display in 256-color mode. Q 5.35: When I capture on Windows in promiscuous mode, I can see packets other than those sent to or from my machine; however, those packets show up with a "Short Frame" indication, unlike packets to or from my machine. What should I do to arrange that I see those packets in their entirety? A: In at least some cases, this appears to be the result of PGPnet running on the network interface on which you're capturing; turn it off on that interface. Q 5.36: I'm capturing packets on a machine on a VLAN; why don't the packets I'm capturing have VLAN tags? A: You might be capturing on what might be called a "VLAN interface" - the way a particular OS makes VLANs plug into the networking stack might, for example, be to have a network device object for the physical interface, which takes VLAN packets, strips off the VLAN header and constructs an Ethernet header, and passes that packet to an internal network device object for the VLAN, which then passes the packets onto various higher-level protocol implementations. In order to see the raw Ethernet packets, rather than "de-VLANized" packets, you would have to capture not on the virtual interface for the VLAN, but on the interface corresponding to the physical network device, if possible. See the Ethereal Wiki item on VLAN capturing for details. Q 5.37: How can I capture raw 802.11 packets, including non-data (management, beacon) packets? A: That depends on the operating system on which you're running, and on the 802.11 interface on which you're capturing. This would probably require that you capture in promiscuous mode or in the mode called "monitor mode" or "RFMON mode". On some platforms, or with some cards, this might require that you capture in monitor mode - promiscuous mode might not be sufficient. If you want to capture traffic on networks other than the one with which you're associated, you will have to capture in monitor mode. Not all operating systems support capturing non-data packets and, even on operating systems that do support it, not all drivers, and thus not all interfaces, support it. Even on those that do, monitor mode might not be supported by the operating system or by the drivers for all interfaces. NOTE: an interface running in monitor mode will, on most if not all platforms, not be able to act as a regular network interface; putting it into monitor mode will, in effect, take your machine off of whatever network it's on as long as the interface is in monitor mode, allowing it only to passively capture packets. This means that you should disable name resolution when capturing in monitor mode; otherwise, when Ethereal (or Tethereal, or tcpdump) tries to display IP addresses as host names, it will probably block for a long time trying to resolve the name because it will not be able to communicate with any DNS or NIS servers. There are FAQ items below with information on capturing in monitor mode on Linux, FreeBSD, and NetBSD. On Windows, you will not be able to capture in monitor mode on any interfaces, and you might not be able to capture in promiscuous mode, either. You might have some success in promiscuous mode with Centrino interfaces, although you will need Ethereal 0.10.6 or later in order to have the non-data packets recognized and properly dissected. You will not be able to capture in monitor mode on any other platforms (including Mac OS X). You might be able to capture in promiscuous mode, but this won't capture non-data packets. Q 5.38: How do I capture on an 802.11 device in monitor mode on Linux? A: Whether you will be able to capture in monitor mode depends on the card and driver you're using. See this page of Linux 802.11b information for details on 802.11b wireless cards, including information on the chips they use, and see this page of Linux 802.11b+/a/g information for details on 802.11b+, 802.11a, and 802.11g wireless cards, including information on the chips they use. Cisco Aironet cards: On Linux with the driver in the 2.4.6 through 2.4.19 kernel: 1. Put the card into monitor mode with the command echo "Mode: rfmon" >/proc/driver/aironet/interface/Config. If you want to capture traffic for any BSS rather than just the BSS with which the card is associated, use "Mode: y" rather than "Mode: rfmon". 2. When the capture completes, turn off monitor mode with the command echo "Mode: ess" >/proc/driver/aironet/interface/Config. On Linux with the driver in the 2.4.20 or later kernel, or with the CVS drivers from the airo-linux SourceForge site, you will have to capture on the wifiN interface if your Aironet card is ethN, after running the commands listed above. In all of those cases, Ethereal would have to be linked with libpcap 0.7.1 or later; this means that most Ethereal binary packages won't work unless they're statically linked with libpcap 0.7.1 or later, or they're dynamically linked with libpcap and your system has a libpcap 0.7.1 or later shared library installed (note that libpcap source package from tcpdump.org does not build shared libraries). Some binary packaging mechanisms might make it difficult to install Ethereal binary packages built to depend on older libpcap binary packages if you have a newer libpcap binary package installed; the installer programs for those packaging mechanisms might support disabling dependency checking so that they will install Ethereal even though a newer version of libpcap is installed. Cards using the Prism II chip set: You can capture raw 802.11 packets with Prism II cards on Linux systems with the 0.1.14-pre6 or later version of the linux-wlan-ng drivers (see the linux-wlan page, and the linux-wlan-ng tarball directory), or with the hostap driver for Prism II/2.5/3. Those require either Solomon Peachy's patch to libpcap 0.7.1 (see his libpcap-0.7.1-prism.diff file, or his RPMs of that version of libpcap), or the current CVS version of libpcap, which includes his patch (download it from the "Current Tar files" section of the tcpdump.org Web site). If you apply his patches to libpcap 0.7.1 and rebuild and install libpcap, or if you build and install the current CVS version of libpcap, you would have to rebuild Ethereal from source, linking it with that new version of libpcap; an Ethereal binary package would not work. Ethereal binary packages might work if you install the libpcap-0.7.1-1prism.i386.rpm RPM, as it might install a libpcap shared library in place of the one on your system. With the linux-wlan-ng driver, you should: 1. Put the card into monitor mode with the command wlanctl-ng interface lnxreq_wlansniffer enable=true. You should request 802.11 headers by adding to that command the option prismheader=true or, if supported, wlanheader=true; the latter might require libpcap 0.8.1 or later. You can also set the channel to monitor by adding the argument channel=channel_number to that command. 2. When the capture completes, turn off monitor mode with the command wlanctl-ng interface enable=false. You might also have to turn 802.11 headers off with prismheader=false or wlanheader=false. See the wlan-ng FAQ for additional information, although note that it does not appear to be up-to-date. With the hostap driver, you should: 1. Put the card into monitor mode with the command iwpriv interface monitor mode, where mode is 2 or 3 (mode 3 would require libpcap 0.8.1 or later). 2. When the capture completes, turn off monitor mode with the command iwpriv interface monitor 0. Orinoco Silver and Gold cards: On Linux systems, the current version of the SourceForge orinoco_cs driver should support monitor mode. There also exist patches to earlier versions of the Orinoco driver, on the Orinoco Monitor Mode Patch Page, to add support for monitor mode. You will have to determine which version of the driver you have, and select the appropriate patch, if one is necessary. Note that the page indicates that not all versions of the Orinoco firmware support this patch. It says, for some versions of the patch, "This patch should allow monitor mode with v8.10 firmware (untested w/ 8.42);" if you have version 8.10 or later firmware on your Orinoco cards, you might have to use those patches, with the corresponding versions of the Orinoco driver, in order to run in monitor mode. That patch is written for the drivers included with the pcmcia-cs drivers, but works equally well for the Orinoco drivers provided with Linux kernels up to 2.4.20. To apply a patch to your kernel drivers, simply copy the orinoco-09b-patch.diff file to the /usr/src/linux/drivers/net directory and patch according to the directions on the Orinoco Monitor Mode Patch Page. You can double- check the version of the Orinoco drivers that shipped with your kernel by examining the first few lines of the orinoco.c file. The Orinoco patches and SourceForge driver require either Solomon Peachy's patch to libpcap 0.7.1 (see his libpcap-0.7.1-prism.diff file, or his RPMs of that version of libpcap), or the current CVS version of libpcap, which includes his patch (download it from the "Current Tar files" section of the tcpdump.org Web site). If you apply his patches to libpcap 0.7.1 and rebuild and install libpcap, or if you build and install the current CVS version of libpcap, you would have to rebuild Ethereal from source, linking it with that new version of libpcap; an Ethereal binary package would not work. Ethereal binary packages might work if you install the libpcap-0.7.1-1prism.i386.rpm RPM, as it might install a libpcap shared library in place of the one on your system. With a driver that supports monitor mode, you should: 1. Put the card into monitor mode with the command iwpriv interface monitor mode channel_number, where mode is 1 or 2, and channel_number is the number of the channel to monitor. 2. When the capture completes, turn off monitor mode with the command iwpriv interface monitor 0. Cards with the Texas Instruments ACX100 chipset: You can capture raw 802.11 packets with ACX100 cards on Linux systems with the ACX100 OSS drivers available from the ACX100 wireless network driver project SourceForge site. With that driver: 1. Put the card into monitor mode with the command iwpriv interface monitor 2 channel_number, where channel_number is the number of the channel to monitor. 2. When the capture completes, turn off monitor mode with the command iwpriv interface monitor 0. Cards with Atheros Communications chipsets: You can capture raw 802.11 packets with AR5K cards on Linux systems with the v5_ar5k or madwifi drivers. For the v5ar5k driver you will need the Linux wireless-tools version 25 or higher to put the card into monitor mode. If you're using the madwifi driver, you can put the card into monitor mode using iwconfig interface mode monitor, followed by iwconfig interface channel channel to select a channel (if needed). Other cards: It might be possible to capture in monitor mode on other cards. If so, please supply us with information on how to do so, so that we can incorporate that information into this FAQ in the future. Q 5.39: How do I capture on an 802.11 device in monitor mode on FreeBSD? A: On FreeBSD 5.2 and later, you should be able to capture in monitor mode on 802.11 interfaces supported by the wi and acx drivers, if Ethereal is linked with libpcap 0.8.1 or later, and on 802.11 interfaces supported by the an driver, if Ethereal is linked with libpcap 0.7.1 or later. For cards supported by the wi and acx drivers, you should: 1. Put the card into monitor mode with the command ifconfig interface monitor. You can also set the channel to monitor by adding the argument channel channel_number to that command. 2. When you start the capture, in Ethereal select "802.11" as the "Link-layer header type", and in Tethereal add the command-line argument -y 802.11. 3. When the capture completes, turn off monitor mode with the command ifconfig interface -monitor. For cards supported by the an driver, you should: 1. Put the card into monitor mode with the command ancontrol -i interface -M flag, where flag should be the sum of: + 1, to turn monitor mode on; + 2, if you want to capture traffic from any BSS rather than just the BSS with which the card is associated; + 4, if you want to see beacon packets (capturing beacon packets increases the CPU requirements of capturing). 2. When the capture completes, turn off monitor mode with the command ancontrol -i interface -M 0. Don't add 8 in to flag; Ethereal currently doesn't support the full Aironet header. On FreeBSD 4.6 through 5.1, you should be able to capture in monitor mode on 802.11 interfaces supported by the an driver, but not on any other interfaces; see the instructions for FreeBSD 5.2 or later for those cards. In FreeBSD 4.5 and earlier, you will not be able to capture in monitor mode on 802.11 interfaces (no drivers supported it prior to 4.5, and in 4.5 the an driver had bugs that caused packets not to be captured correctly). Q 5.40: How do I capture on an 802.11 device in monitor mode on NetBSD? A: On NetBSD 2.0-beta and later, you should be able to capture in monitor mode on 802.11 interfaces supported by the wi and acx drivers, if Ethereal is linked with libpcap 0.8.1 or later. The instructions are the same as for FreeBSD 5.2 and later. Q 5.41: I'm trying to capture 802.11 traffic on Windows; why am I not seeing any packets? A: At least some 802.11 card drivers on Windows appear not to see any packets if they're running in promiscuous mode. Try turning promiscuous mode off; you'll only be able to see packets sent by and received by your machine, not third-party traffic, and it'll look like Ethernet traffic and won't include any management or control frames, but that's a limitation of the card drivers. Q 5.42: I'm trying to capture 802.11 traffic on Windows; why am I seeing packets received by the machine on which I'm capturing traffic, but not packets sent by that machine? A: This appears to be another problem with promiscuous mode; try turning it off. Q 5.43: How can I capture packets with CRC errors? A: Ethereal can capture only the packets that the packet capture library - libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of libpcap on Windows - can capture, and libpcap/WinPcap can capture only the packets that the OS's raw packet capture mechanism (or the WinPcap driver, and the underlying OS networking code and network interface drivers, on Windows) will allow it to capture. Unless the OS always supplies packets with errors such as invalid CRCs to the raw packet capture mechanism, or can be configured to do so, invalid CRCs to the raw packet capture mechanism, Ethereal - and other programs that capture raw packets, such as tcpdump - cannot capture those packets. You will have to determine whether your OS needs to be so configured and, if so, can be so configured, configure it if necessary and possible, and make whatever changes to libpcap and the packet capture program you're using are necessary, if any, to support capturing those packets. Most OSes probably do not support capturing packets with invalid CRCs on Ethernet, and probably do not support it on most other link-layer types. Some drivers on some OSes do support it, such as some Ethernet drivers on FreeBSD; in those OSes, you might always get those packets, or you might only get them if you capture in promiscuous mode (you'd have to determine which is the case). Note that libpcap does not currently supply to programs that use it an indication of whether the packet's CRC was invalid (because the drivers themselves do not supply that information to the raw packet capture mechanism); therefore, Ethereal will not indicate which packets had CRC errors unless the FCS was captured (see the next question) and you're using Ethereal 0.9.15 and later, in which case Ethereal will check the CRC and indicate whether it's correct or not. Q 5.44: How can I capture entire frames, including the FCS? A: Ethereal can only capture data that the packet capture library - libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of libpcap on Windows - can capture, and libpcap/WinPcap can capture only the data that the OS's raw packet capture mechanism (or the WinPcap driver, and the underlying OS networking code and network interface drivers, on Windows) will allow it to capture. For any particular link-layer network type, unless the OS supplies the FCS of a frame as part of the frame, or can be configured to do so, Ethereal - and other programs that capture raw packets, such as tcpdump - cannot capture the FCS of a frame. You will have to determine whether your OS needs to be so configured and, if so, can be so configured, configure it if necessary and possible, and make whatever changes to libpcap and the packet capture program you're using are necessary, if any, to support capturing the FCS of a frame. Most OSes do not support capturing the FCS of a frame on Ethernet, and probably do not support it on most other link-layer types. Some drivres on some OSes do support it, such as some (all?) Ethernet drivers on NetBSD and possibly the driver for Apple's gigabit Ethernet interface in Mac OS X; in those OSes, you might always get the FCS, or you might only get the FCS if you capture in promiscuous mode (you'd have to determine which is the case). Versions of Ethereal prior to 0.9.15 will not treat an Ethernet FCS in a captured packet as an FCS. 0.9.15 and later will attempt to determine whether there's an FCS at the end of the frame and, if it thinks there is, will display it as such, and will check whether it's the correct CRC-32 value or not. Q 5.45: Why does Ethereal hang after I stop a capture? A: The most likely reason for this is that Ethereal is trying to look up an IP address in the capture to convert it to a name (so that, for example, it can display the name in the source address or destination address columns), and that lookup process is taking a very long time. Ethereal calls a routine in the OS of the machine on which it's running to convert of IP addresses to the corresponding names. That routine probably does one or more of: * a search of a system file listing IP addresses and names; * a lookup using DNS; * on UNIX systems, a lookup using NIS; * on Windows systems, a NetBIOS-over-TCP query. If a DNS server that's used in an address lookup is not responding, the lookup will fail, but will only fail after a timeout while the system routine waits for a reply. In addition, on Windows systems, if the DNS lookup of the address fails, either because the server isn't responding or because there are no records in the DNS that could be used to map the address to a name, a NetBIOS-over-TCP query will be made. That query involves sending a message to the NetBIOS-over-TCP name service on that machine, asking for the name and other information about the machine. If the machine isn't running software that responds to those queries - for example, many non-Windows machines wouldn't be running that software - the lookup will only fail after a timeout. Those timeouts can cause the lookup to take a long time. If you disable network address-to-name translation - for example, by turning off the "Enable network name resolution" option in the "Capture Options" dialog box for starting a network capture - the lookups of the address won't be done, which may speed up the process of reading the capture file after the capture is stopped. You can make that setting the default by selecting "Preferences" from the "Edit" menu, turning off the "Enable network name resolution" option in the "Name resolution" options in the preferences disalog box, and using the "Save" button in that dialog box; note that this will save all your current preference settings. If Ethereal hangs when reading a capture even with network name resolution turned off, there might, for example, be a bug in one of Ethereal's dissectors for a protocol causing it to loop infinitely. If you're not running the most recent release of Ethereal, you should first upgrade to that release, as, if there's a bug of that sort, it might've been fixed in a release after the one you're running. If the hang occurs in the most recent release of Ethereal, the bug should be reported to the Ethereal developers' mailing list at ethereal-dev@ethereal.com. On UNIX-flavored OSes, please try to force Ethereal to dump core, by sending it a SIGABRT signal (usually signal 6) with the kill command, and then get a stack trace if you have a debugger installed. A stack trace can be obtained by using your debugger (gdb in this example), the Ethereal binary, and the resulting core file. Here's an example of how to use the gdb command backtrace to do so. $ gdb ethereal core (gdb) backtrace ..... prints the stack trace (gdb) quit $ The core dump file may be named "ethereal.core" rather than "core" on some platforms (e.g., BSD systems). Also, if at all possible, please send a copy of the capture file that caused the problem; when capturing packets, Ethereal normally writes captured packets to a temporary file, which will probably be in /tmp or /var/tmp on UNIX-flavored OSes, \TEMP on the main system disk (normally C:) on Windows 9x/Me/NT 4.0, and \Documents and Settings\your login name\Local Settings\Temp on the main system disk on Windows 2000/Windows XP/Windows Server 2003, so the capture file will probably be there. It will have a name beginning with ether, with some mixture of letters and numbers after that. Please don't send a trace file greater than 1 MB when compressed; instead, make it available via FTP or HTTP, or say it's available but leave it up to a developer to ask for it. If the trace file contains sensitive information (e.g., passwords), then please do not send it. Q 5.46: How can I search for, or filter, packets that have a particular string anywhere in them? A: If you want to do this when capturing, you can't. That's a feature that would be hard to implement in capture filters without changes to the capture filter code, which, on many platforms, is in the OS kernel and, on other platforms, is in the libpcap library. In releases prior to 0.9.14, you also can't search for, or filter, packets containing a particular string even after you've captured them. In 0.9.14, you can search for, but not filter, packets that have a particular string; this has been added to the "Find Frame" dialog ("Find Frame" under the "Edit" menu, or control-F). In 0.9.15 and later, you can search for those packets using either the mechanism introduced in 0.9.14 or using the new "contains" operator in filter expressions, which lets you search the entire packet or text string or byte string fields in the packet; the "contains" operator can also be used in expressions used to filter the display. Q 5.47: How do I filter a capture to see traffic for virus XXX? A: For some viruses/worms there might be a capture filter to recognize the virus traffic. Check the CaptureFilters page on the Ethereal Wiki to see if anybody's added such a filter. Note that Ethereal was not designed to be an intrusion detection system; you might be able to use it as an IDS, but in most cases software designed to be an IDS, such as Snort or Prelude, will probably work better. The Bleeding Edge of Snort has a collection of signatures for Snort to detect various viruses, worms, and the like. Please send support questions about Ethereal to the ethereal-users[AT]ethereal.com mailing list. For corrections/additions/suggestions for this web page (and not Ethereal support questions), please send email to ethereal-web[AT]ethereal.com . Last modified: Sun, February 27 2005.