CSS11500 v8.1 STP best practices

Unanswered Question
Mar 20th, 2007


Could some one tell me what is the recommended STP setting for the CSS 11500 plugged to Cisco Catalyst switch? Should it be port fast or not since in the routing and bridging guide it says that Catalyst and CSS doesnt recognize each others BPDU VLAN tagging?


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Syed Iftekhar Ahmed Tue, 03/20/2007 - 11:18

1. Change the catalyst port to "access mode"

2. Enable port fast on ports connected to CSS.

3. Disable stp on CSS when in bridge mode

Syed Iftekhar Ahmed

joquesada Tue, 03/20/2007 - 18:11


I assume you want to configure a trunk between the CAT switch and the CSS given that you are talking about VLAN tagging.

By experience I can tell you that the CSS works well with STP when you don't mess with STP; this given that the CSS runs 802.1q so the CAT switch would see it as a switch running mono-STP.

As rule of thumb, I follow some guidelines when configuring a trunk between a CSS and a CAT switch:

- First, I make sure the CSS is not the STP root by using this command on the CSS: "(config)#bridge priority 65000"

- Second, make sure the same native vlan is set in both sides ( on the CSS the term used is default vlan )

If you are thinking about configuring only access ports instead of trunks, then, port-fast can be considered as long as you make sure that two interfaces aren't on the same VLAN connected to the same switch.


Jose Quesada


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