Sniff 802.1q frames

[monkeyman100]

Help !!

Scenario : Cat2950 switch. fas0/1 has an ip phone connected
fas/048 is a span port monitoring fas0/1

problem : I am trying to determine if traffic sent from my ip phone has .1q tagging with a COS value of 7 added to the frames. I am using Sniffer Pro ver.4.7 - No encapsulation details are reported from the capture. Anyone know how to do this ?...a friend had said that a SPAN port wont see .1q traffic!?!....but i really need to know thats its happening.

Cheers

 

[BuckWeet]

It will see the traffic, I've done it before..

FYI, you shouldn't set the high of a priority on your network, just to give you a reason why, in larger networks you'd want only routing protocols or spanning tree algorithms to be set that high of a CoS/QoS.

Usually you keep your phones set to 3 or 5 for CoS/QoS settings..


As for the traffic, basically you're just going to see a field in the frames for CoS (layer 2 header) and QoS (layer 3 header).

I've done it on Cisco switches, with AVAYA or CISCO IP phones, and they all come through for me...



BuckWeet

 

[monkeyman100]

Thanks for that. Can you tell what sniffer software you used to see frame info ?. I'll also change the COS valus down to 5.

R

 

[BuckWeet]

I've used Sniffer Pro, Etherreal (or Ethereal, one of those 2) and Wildpackets Etherpeek..


BuckWeet


Etherreal is free though.. do a search on google for it..