Spanning Tree

Unanswered Question
Aug 27th, 2010

Hello,

Here is my delima: I have aquired a network with the following configuration:

- 1 Extreme 8810 - core switch - This switch has 8 cisco 4003 & 2 3624 switches connect via fiber backbone

- Spanning tree is enabled on some of the switches and not on others

My dilema:  I am looking for the best way to ensure that spanning tree is configured correctly.

- Is there a best practice guide to follow for step by step configuration

- should I use VTP?

- should I use PortFast ? if so How?

- BPDU ? Can I route the BPDU traffic on a seperat vlan?

As you can see that I am not a spanning tree expert. I am some what familiar as to some of the configuration methods I just need help on making sure everything is properly setup.

Thank you in advance for your cooperation.

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Reza Sharifi Fri, 08/27/2010 - 14:58

Hello,

Here is the config guide with examples you can start with:

http://www.ciscorouters.biz/en/US/docs/switches/lan/catalyst4500/12.1/8aew/configuration/guide/spantree.html

should I use VTP?no

- should I use PortFast ? if so How?yes, on access ports see below

http://www.ciscorouters.biz/en/US/docs/switches/lan/catalyst4500/12.1/8aew/configuration/guide/stp_enha.html

- BPDU ? Can I route the BPDU traffic on a seperat vlan?no

HTH

Reza

Hitesh Vinzoda Fri, 08/27/2010 - 22:24

Hi

Here are few suggestions based on the details provided by you

1. Extreme switch is a core switch and if the link between Extreme and other Cisco switches are layer 2. Make sure that Core switch is a spanning tree root ie.Centre of you network

2. Change the STP priority of core switch to 0 and keep the cisco switches priority to default of 32768

3. Now the Extreme switch is not capable of running PVST as its a Cisco proprietory protocol, you have to run CST or MSTP if supported.

4. Cisco switches may run pvst as its backward compatible... no issues

5. Portfast feature can be enabled on access ports of Cisco switches. use the below command to do so.

          int fa0/1

          spanning-tree portfast  or

          switchport host

6. You shouldnt be using VTP as VTP is a Cisco proprietory protocol and extreme switch may support GVRP, but static configuration of vlan should help and scale better as the size of the network is not that large.

7. As suggested by Reza, you cannot have separate Vlans for BPDU traffic, and that should not be a concern for you.

8. Check throughout the topology that spannig tree root is extreme switch. In case of MST it should be root for all vlans.

HTH

Hitesh Vinzoda

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