VLANS bleeding over on 3750

djbowling · ‎03-21-2008

All, I need help here. I have 3 Cisco 3750's in a triangle configuration, with one switch at each point of my triangle. There are 2 fiber lines that connect each switch. 1 for normal communications, and the other for a backup purpose. I have about 9 different VLANS on each switch.

If i use Windows 2000 Network monitor, to view the traffice on, say VLAN 1. I can see ipaddress that are supposed to be only on VLAN 2-9. I call this VLAN bleeding. Not sure if its the correct term or not.

Anyways. Hows does one go about troubleshooting this type of problem? I have ruled out the physical hardware to be the cause and now im trying to find an answer in the 3750's.

Please advise.

i-kendall · ‎03-27-2008

What sort of traffic are you seeing ? And you are not monitoring a trunk port are you ?

If you really are seeing this it sounds like a probable configuration problem. Post them here and we may get a better idea of the cause.

sundar.palaniappan · ‎03-27-2008

I agree with the previous poster we need more information to better identify the problem.

However, I have a thought why you may be seeing traffic in vlan 1 that you aren't supposed to be seeing. The default native vlan on 802.1q trunk is vlan 1. There may have been untagged frames that arrived on the trunk ports that would have been put into vlan1. That's the only thing I can think of at this time.

HTH

Sundar