Spanning-Tree Case

[AhmedElGarf]

I need to understand whats the spanning-tree actions in below cases

A) if port 1 on both switches Access Vlan 100 and port 2 in both cases access vlan 200

and the running pvst on both swicthes , will the spanning tree block any links ? as the vlans carried in both links are different ? 

B) if all interface mode is Trunk but in the the upper link allowed vlan is 100 on bothe swites and allowed vlan is 200 in lower in in both switches? what is the stp action in this case and why?

thx

[EduardR]

Hi,

I've used something similar to your configuration to migrate VLANs from one infastructure to another and have not encountered problems. In principle, if you are using PVST or RPVST, both links will be in forwarding state, as lon as each port has only one permitted vlan.

In both case, for the VLAN 100 and 200 there are not closed loops that trigger STP to block any port, but in the second case, is highly probable that the native VLAN will be in forwarind in 1 port and in blocking in the another one.