Local SPAN voice VLAN

[limtohsoon]

Hi Sir,

I have an IP phone connected to a trunk port. I configured Local SPAN to sniff traffic to/from the phone, as follows:

!

interface Gig 0/5

desc *** Connection to IP Phone ***

switchport trunk encapsulation dot1q

switchport trunk native vlan 10

switchport mode trunk

switchport voice vlan 11

!

interface Gig 0/4

desc *** Connection to Ethereal Packet Sniffer ***

!

monitor session 1 source interface gig 0/5 both

monitor session 1 destination interface gig 0/4

!

I'd like to see the dot1Q tags for voice VLAN 11 in the frames, but I don't see them in the sniffer trace. What I saw are only untagged frames to/from the phone. Is this normal?

Then, how can I accomplish my objective?

Please help.

Thank you.

B.Rgds,

Lim TS

[Amit Singh]

Hi Lim,

Which switch is this and what IOS You are running? you can use "encapsulation" command in the destination session configuration to see the encrypted packets. Please remove the SPAN session with " no monitor session all command configure it again with encapsulation enabled.

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3750/12235se/scg/swspan.htm#wp1036816

HTH,Please rate if it does.

-amit singh

[mrarahman]

Hi Lim,

You can use this command to capture dot1q tags in the capture as follows:

monitor session 1 source interface gig 0/5 both

monitor session 1 destination interface gig 0/4 encapsulation dot1q

Cheers

AR