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New Member

Introducing new switch to TRUNKED network

I have 2 old 3550s acting as network cores, they are running HSRP together, and there is a trunk link from each core going to each leaf switch in my network for redundancy, stp controls the active/standby links...

I am about to replace an old 2950 leaf switch with a new 3750 and I don't want this switch to become the root for all VLANs in the topology, just some that are mainly local to this switch - any advice?

Also, would there be any other things that I should be careful with or aware of before doing this? (no worries with VTP, running transparent mode everywhere)


Hall of Fame Super Bronze

Re: Introducing new switch to TRUNKED network

Configure one 3550 as spanning tree root primary and the other as secondary with the following command:

(config)#spanning-tree vlan [vlanid list] root primary | secondary

New Member

Re: Introducing new switch to TRUNKED network


If you need to tune STP you can use a number of different methods. Yo can manually set the STP priority of your switches. The lower the number to more chance that it will be the root. Here are some commands:

spanning-tree priority 1 (default is 32768) this will set a switch to be the root as long as every other switch has a default priority or higher.

If you want the switch to look at all the priority numbers on the Spanning-Tree and decide for you use:

spanning-tree vlan root primary

Pls rate if this helps.


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