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STP and VLAN tagging

Hello everyone, I have two switches that are tagged and trunked together with two connections. I want to manually configure the STP priorities on the VLANs that are on these switches to ensure a nice deterministic convergence. I understand that each VLAN runs its own instance of STP and is seperately configured at the VLAN level. But how do I configure the priority for the VLAN that is trunked between the switches? Do I configure the same priority in each switches' configuration for the VLAN that is on both switches?

Thanks!

Reply to
uofitorn
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The switch with the lowest priority will be the root switch. Once you've figured out which switch you want to be the root then use the "set spantree priority" command on it to make it less than the default of 32768 (assuming the other switches haven't been changed). It's a good idea also to have a backup root switch. Cisco uses Per-VLAN spanning tree (PVST). The initial version of .1q specified using a single instance of STP for all VLANs but they may have added support for multiple instances. Maybe someone else knows this.

Reply to
Brad

It depends on how you want it to work. For my purposes, I want a single switch to be the root bridge. Therefore, I set the priority on that switch and that is all that needs to be done. For example:

spanning-tree vlan 10,20,30,40,50,60 priority 4096

If you don't set this on a switch, it will use the default prio+mac address for the bridge and will calculate automatically. Setting the same priority for a vlan between the switches would be the same as not setting the priority at all. If you have certain areas that you want to have separate root bridges, set the priority for the particular vlans on that device.

That said... With only two switches, you don't really need spanning-tree unless you are using two uplinks for redundancy. Even so, I'm not sure I would even care about the root bridge as it really wouldn't make any difference.

Hope that helps,

Jim

Reply to
Scooby

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