Spanning tree in a single backbone switch

[john smith]

Dear Friends,

how i can configure the spanning tree while i have such design. that i have a 2X3750 in a stack acting as core switch=> one access switch connected to this core switch with 2 uplinks.

thanks

[Jon Marshall · Accepted solution]

You configure a MEC (Multichassis Etherchannel) trunk from the access switch to the 3750 stack ie. spread the physical ports between the stack members and then all links from the access layer switch are forwarding.

STP sees the etherchannel as a single logical connection and will not block any ports. You should still run STP as a failsafe to protect against devices being connected that could create a loop.

You should set the STP priority on the 3750 stack to be lower than the default to make sure that the 3750 stack is STP root for all vlans.

Jon

[john smith]

Thanks for your reply Jon

in 2nd option are you talking about this?

spanning-tree vlan 1-4094 priority 0

thanks

[JohnTylerPearce]

Waseemfarrakh,

That's what he's saying. But since most modern switches, incorporate the Extended System-ID enhancement, the priorites of your BID from that switch, will be Priority = (Priority of 0 + VLAN-ID)

So if you have a VLAN of 10 it will have a priority of 10. Also your priorties will need to be in multiples of 4096 most likely.

Hope that helps some.

[john smith]

Thanks guys for you help,

i guess this will help.

thanks