How will PVST behave in a situation in which there are two switches connected to each other via access switchports which have different VLANs assigned to them?


[Switch 1] Port with "Access Vlan 100" <----> Port with "Access Vlan 200" [Switch2]

Traffic from switch 1, on VLAN 100 will arrive to switch 2 untagged and become part of switch 2's VLAN 200, and vice versa.

But how will PVST behave in this situation, considering the VLANs do not match on the link between the 2 switches?

I am not intending to create this situation on purpose, just curious about how PVST will behave in this situation.


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1 Answer 1


You will get Native VLAN Mismatch errors. The two VLANs will now be one layer-2 domain instead of two, and this may be a problem, or not, depending on how the rest of the network is configured and connected.

If the ports have DTP enabled, and at least one side is Desirable, a trunk will form.

If you have BPDU guard enabled on either port, it will be errdisabled.

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