Wireshark-users: Re: [Wireshark-users] Capturing VLAN tags with Wireshark

Date: Thu, 10 Jul 2008 09:59:10 -0400
Maybe I should have specified a little bit more. 

Source:

Router(config)#monitor session 1 source interface GigabitEthernet 6/1
both

Destination:

Router(config)#monitor session 1 destination interface GigabitEthernet
4/48

Destination port config:

Router(config)#interface gi4/48
Router(config)#switchport
Router(config)#switchport trunk encapsulation dot1q
Router(config)#switchport mode trunk
Router(config)#switchport nonegotiate


-----Original Message-----
From: wireshark-users-bounces@xxxxxxxxxxxxx
[mailto:wireshark-users-bounces@xxxxxxxxxxxxx] On Behalf Of Steve
Bertrand
Sent: Thursday, July 10, 2008 9:42 AM
To: wireshark-users@xxxxxxxxxxxxx
Subject: [Wireshark-users] Capturing VLAN tags with Wireshark

Hi everybody,

I've got a handful of VLANs (802.1q) running over a Cisco infrastructure

and I'm trying to capture the Ethernet frames on a switch trunk port 
while retaining the VLAN information contained within.

 From what I can tell, in order to be able to do a port monitor on a 
Catalyst switch to sniff VLAN traffic, I have to assign the monitor port

as a switchport access within a specific VLAN. I assume that when I do 
it this way, the VLAN tag is being stripped off before the monitor port 
hands off the packet to Wireshark. Is this correct?

Am I missing something obvious? I'd just like to be able to monitor ALL 
traffic that is ingress/egress on a specific trunk port for all allowed 
VLANs on that trunk, all the while retaining the VLAN information within

the frame.

Thanks for any advice.

Steve
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