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Optimizing STP

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goosed

MIS
Jan 5, 2007
44
US
I have STP enabled on my switches, but I am not sure if it is optimized correctly. Here is my scenario: 3 stacked 3750 switches, with 7 VLANs. When I run a spanning-tree summary, I show 329 ports forwarding, with 330 ports with STP active. There is only 1 port blocking. When I run spanning-tree root, each VLAN does show a Root ID, but only two of them have assigned Root Ports. Is this correct?
 
Judging from the details of your post, you have the three 3750's cabled together in a triangle topology??

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
- ColdFlame (vbscript forum)
 
All three are stacked together to show up as one.
 
For stackwise, each switch in the stack will have its own STP instance per-vlan, although all port states are known by the master.

How specifically are you trying to optimize STP? Form the sounds of it, are you just trying to confirm if more ports should be blocking? If there is no switching loop, then the number of ports in a blocking state would typically be correct.

Also you'll only see root ports on two of the switches because they're not the root bridge (those ports face towards the root bridge). The STP root bridge will have all of its ports in a forwarding state as designated ports for their respective segments.

You may want to read up on Stackwise here, specifically under the "Subordinate Switch Activities" section:

CCNP, CCDP
 
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