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vlan mismatch

vlan mismatch

vlan mismatch


We have a vlan mismatch between our main office and test networks.

The native vlan in the office is vlan1. In the test network their main subnet is vlan1, and the office subnet is vlan3.

I'm trying to link the two networks together and avoid broadcast traffic from the test network. I thought of setting the native vlan for the trunk to vlan3, so office traffic is untagged. How will the office switch then deal with vlan1 tagged traffic coming through the trunk (when the office switch is vlan1 native)?



RE: vlan mismatch

Only allow VLAN3 on the Test network switch trunk.

What kind of switches do you have?

RE: vlan mismatch


It is not a major problem to have two different native vlans on a trunk, although you will see errors on the switch console but it won't stop the trunk from coming up. I take it your encapsulation is dot1q since native vlans are not more than mere cosmetic in isl. You could just permit vlan 3 on the trunk using the command


switchport trunk allowed vlan 3 

and that would effectively stop broadcast from the downstream test network on vlan1 from saturating your trunk link but cdp, vtp and stp would continue to work.


RE: vlan mismatch

Thanks for the replies. I need both vlans allowed down the trunk.

The switches I have don't support vlan retagging. We're now planning on removing office network devices from the test side of the network ( and routing it instead )


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