Third situation, and most likely is that the switch itself is stripping
VLAN tagging. Check with the switch vendor on how to pass this through;
you're likely to have to set the Dell NIC to the relevant VLANs.
Randy Grein
Network Engineer
"Mike Landman" <mlandman@xxxxxxxxxxxxxxxxxxxxx>
Sent by: wireshark-users-bounces@xxxxxxxxxxxxx
05/24/2007 11:39 AM
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[Wireshark-users] question on seeing the vlan tags on linux
Hi,
I’m not seeing some VLAN tags that I think should exist. I’m running
wireshark on a Dell server blade running linux. The Ethernet adapter is
NOT configured for VLANs in any way. It’s connected to a switch that has
port mirroring configured to send packets to the Dell.
I receive the packet, but it looks as if the eth type and vlan ID (i.e.
the entire vlan tag) is stripped.
Reading the FAQ and the wiki, I see that this is expected behavior in
either of the following cases:
(1) Under Linux, if I have a vlan configured Ethernet adapter, then
the VLAN tag might be stripped before going up the stack.
(2) Under Windows, the drivers for some broadcom/intel adapters will
strip out the vlan tag, and a registry key needs to be tweaked to allow
that data to be visible higher up the stack.
In my scenario, I’m running Linux, there is no VLAN configuration, yet the
packets still seem to have the 1st VLAN tag removed. It’s 802.1ah, so I
expect to see 2 VLAN tags. I only see one. It’s as if the first vlan tag
is removed, leaving the second one in the place that the first would
otherwise be.
Has anyone ever seen this occur under Linux, when capturing directly from
eth0 (i.e. not eth0.100?)
Regards,
-mike_______________________________________________
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