STP and redundant links

[iores]

Hi,

If switch A and switch B are connected with 2 identical trunks, one will get blocked by STP.

However, for example, if I allow only Vlan 10 on trunk 1, and disallow Vlan 10 on trunk 2, both trunk will be active.

Is that right?

[MHM Cisco World]

Why you do that 

Instead use PVST and SW vlan STP priority to load balance between two trunk.

Your way is not correct.

MHM

[MHM Cisco World]

https://www.cisco.com/c/en/us/support/docs/lan-switching/spanning-tree-protocol/10555-15.html

This doc. Explain how you can config 

MHM

[iores]

Because I don't want to mix LAN and WAN traffic (VLAN 10) on the same physical link.

[MHM Cisco World · Accepted solution]

If you dont allow one vlan in trunk that have two vlan' why trunk use ? You can use access port which have only one vlan.

MHM

[Joseph W. Doherty · Accepted solution]

Yes, that's correct because Cisco's STP is per VLAN.

In a real network it would be better to allow VLANs to use both trunks, for redundancy.  You can configure PVSTP so that with both trunks "up", VLAN 10 will use one, as its better path, while other VLAN(s) prefer the other trunk.  (Being able to selectively direct VLANs to use different redundant links is the feature of PVSTP.)