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Best method to block Vlan port with spanning tree

In a complex Switch Network I lick to configure the vlan ports how should normally blocked by spanning tree with a bad priority value. I have the concept the Backbone links should never blocked until the Backbone itself is redundant and has a better priority than the normal value.

On the access switches are the half vlans normally blocked on one of both uplinks with a more bad priority value. The question: exist a better method or possibility to combine two methods or values to get a twostep concept? First is one defined port blocked else a second port?

Tanks for your ideas.

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Accepted Solutions
Cisco Employee

Re: Best method to block Vlan port with spanning tree

There are 2 ways to manually decide which ports will be blocking. The first one is to tune the port priority. That method is used when you have parallel links between switches for instance as shown at the following URL:

http://www.cisco.com/warp/customer/473/15.html

You could also tune the port cost per VLAN but that method will have an impact on the whole spanning-tree as the cost will be carried in the BPDUs across the network while the priority is locally significant.

Another way to choose the form of your spanning-tree is by placing your root switch for a specific VLAN is a strategic place.

More information on spanning-tree can be found here:

http://www.cisco.com/warp/customer/473/#SpanningTree

1 REPLY
Cisco Employee

Re: Best method to block Vlan port with spanning tree

There are 2 ways to manually decide which ports will be blocking. The first one is to tune the port priority. That method is used when you have parallel links between switches for instance as shown at the following URL:

http://www.cisco.com/warp/customer/473/15.html

You could also tune the port cost per VLAN but that method will have an impact on the whole spanning-tree as the cost will be carried in the BPDUs across the network while the priority is locally significant.

Another way to choose the form of your spanning-tree is by placing your root switch for a specific VLAN is a strategic place.

More information on spanning-tree can be found here:

http://www.cisco.com/warp/customer/473/#SpanningTree

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