Monitoring VLAN traffic

[lneill]

I heard somewhere that there is a way to turn one port on a switch with VLANs to promiscuious mode... I believe was the term. I basically to be able to monitor all of VLAN traffic from both of the two VLANs I have configured on my 2900. Is there a way to do that?

[jamey]

You may be talking about SPAN. Here's a URL about the 2900 implementation of SPAN.

http://www.cisco.com/en/US/products/hw/switches/ps605/products_configuration_guide_chapter09186a008007d7db.html#xtocid816522

Note, on the 2900 at least, you cannot monitor ports in a different VLAN that the monitor port. I suggest maybe (if possible) monitor all VLANA ports on say port 1 of the switch and all VLANB ports on port 2 of the switch. Then connect ports 1 and 2 to a hub and connect your monitoring station to the hub and you should be able to see VLANA and VLANB traffic with your PC's NIC in promiscuious mode.

-HTH

[lneill]

Great thanks! I will try that.