Avoid spanning-tree timer in square topology

Unanswered Question
Nov 5th, 2008


I must connect two Cisco 7606 with two Cisco Catalyst 4506 at level 2 only. The final topology is a square. The Catalyst 4506 are connected to three routers in dual-homing and have a Port-Channel between them. When I connect the 4506 to the 7606 I have to transport a VLAN only so the trunk is not needed. I'd like to avoid the spanning tree timer calculation when I plug the cable because the router are in a live network and I'm scared to lost traffic.

I thought to configure the port connected to the router with span tree portfast and remove the vlan from the trunk back-to-back. Is that a good idea or exist other better solutions?

I have this problem too.
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satish_zanjurne Wed, 11/05/2008 - 06:06

Can you paste the Diagram of what is the current setup & what will be the setup after change ?

Also take downtime or scheduled maintenance , to do this , to be on safer side.

urbinir Wed, 11/05/2008 - 06:22

Hi I add the complete topology. The port connected between 4506 and router are in Access mode and between the 4506 there is an EtherChannel. I might decide how to configure the port connected between the 4506 and 7606 and how to decrease the spanning tree calculation problem when I plug the cables

Amit Singh Wed, 11/05/2008 - 06:25

Well the best of this would be configure the ports as L3 ports to bring them up immediately. You can run a routing protocol and you have auto-matic load-balancing with redundancy/Fail-over for you in the network.

-amit singh

urbinir Wed, 11/05/2008 - 06:38

good thing but i cannot because the 7600, in the future, will became a LAN aggregator with routers directly connect to it without the Catalyst 4506. The Catalyst 4506 remains only for a transitory period


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