Reusing Vlan ID's at Different Locations.

[jakehabart]

I was wondering if there is any problems with reusing Vlan numbers at differnt locatins. Each location is seperated by a router. I am not sure if the 802.1Q tags will propogate over layer 3 or if they are stripped off.

thx

[Kevin Dorrell]

That should not be a problem at all. As long as the locations are separated by a router, and there is not chance that the VLANs with the same ID can meet in the same switch, then you will be OK. The tags will not normally pass through a layer-3 router.

Kevin Dorrell

Luxembourg

[jakehabart]

thx

thats what I assumed but beter safe than sorry.

[alex.walker]

Also, 802.1Q tags are only Layer 2 switched over Ethernet trunks. If you just use standard "access" links instead of trunks, you can use different VLAN numbers on each switch (even for the same VLAN (broadcast domain)). No need to isolate with a router.

Might make things a bit harder to manage though!

[milan.kulik]

But this is a wrong practise which I wouldn't recommend unless absolutely necessary!

You have to remember "VLAN2 on switch1 is connected to VLAN45 on switch2 which is connected to VLAN33 on switch3"...

Big chance for bringing troubles, I'm afraid.

BTW, you'll get an error message to your syslog ("native VLAN mismatch" which is even more confusing) when using CDP2 in this case.

My opinion is you should NEVER interconnect VLANs on L2.

Regards,

Milan