If you are a registered user of VMware on Linux, you can contact their
support staff via e-mail and ask for a libpcap patch which will allow
you to sniff the virtual NIC of your virtual machine.
vmware configures 4 devices, /dev/vmnet[0-3].
/dev/vmnet0 is your ethernet bridge, giving your virtual machine its
own MAC address on your physical ethernet LAN.
/dev/vmnet1 is for host-only networking. Your host OS will be routing IP
packets between the physical LAN and the guest OS. When up and running,
you'll see a 'vmnet1' interface from 'ifconfig'.
/dev/vmnet2 and /dev/vmnet3 act as hubs for virtual machines, but are
not connected to anything else. That is, the VM's that are connected
to these devices can talk to each other (if connected to the same
virtual "hub"), but not to the outside world, or to your host OS
(as far as I understand).
With the patch from VMware, you can sniff the packets on these
network devices. Note the distinction between "network device", where a
device driver file exists in /dev, and "interface", which is a namespace
private to the kernel (not on the filesystem). You have to supply the
full pathname of the device to Ethereal (i.e., "/dev/vmnetN").
When vmnet1 is up, you will be able to select it from the list of
interfaces, since it will have both a device name (/dev/vmnet1) and
an interface name "vmnet1"
See also http://www.vmware.com/products/scenarios/networks.html