Error when configuring SPAN to capture trunk port data with 802.1q tag

[Difan Zhao]

Hello everybody,

When I configure SPAN on my 3750 switch, it gives me this error:

"

% Warning: One or more specified dest port does not support requested encapsulation.

"

The command I use to configure SPAN is:

(config)#monitor session 1 destination interface Fa1/0/24 encapsulation dot1q

I am using WireShark as the packet sniffer and I have configured my Ether Card on my PC to accept vlan tags however I still can't see the tags from the captured data...

I also tried to configure f1/0/24 as a trunk port but I still get the same error... I will very much appreciate any help or advice! Thanks!

Difan

[amikat · Accepted solution]

Hi,

Your command should read as:

monitor session 1 destination interface Fa1/0/24 encapsulation replicate,

as documented e.g. at:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_44_se/command/reference/cli1.html#wp9700521,

please see the Usage Guidelines part,

Best regards,

Antonin

[Difan Zhao]

Thanks a lot Amikat! It works now!