config bpdu's xmitted

Unanswered Question
Nov 8th, 2007

I have a 6506 and when doin the sh spantree stat port command, the "config bpdu's xmitted" is very high (224129002)...and seems to increase very fast (couple hundreds a minute)...is this a normal behavior ? This 6506 cpu is always at 75 % and the stbpdu process seems to be at 35 % all the time...my network seems to be unstable too...we have about 50 switch (3548,3508,2950,2960...) and about 50 vlan

Any hint for me ?

Thx

I have this problem too.
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paul.matthews Thu, 11/08/2007 - 23:26

The standard BPDU timer is 2 secs - ie one BPDU every two secs. any switch that has been up for any length of time should have a high count on BPDU TX.

It does sound like you may have some issue with spanning tree.

How is your network built? Do you manually prune VLANs? use the switch trunk command to only allow VLANs where they need to go.

With 50 switches you also need to make sure the actual topology is sensible - the core switches do have the priority configured such that they are the root and backup root, don't they? rootguard can help with rogue root bridges.

What about portfast? make sure that is configured on all user ports. There are two main effects with that - the obvious one is the immediate trasition to forwarding, the other is that it suppresses the messages sent to the root bridge when a port goes up or down, which will reduce the workload on the root (and many other switches).

Francois Tallet Thu, 11/08/2007 - 23:34

What mode are you running. PVST and Rapid-PVST send one BPDU per port and per vlan every two second by default. During reconvergence time, the rate can go up to 6 BPDU per seconds.

How many trunks do you have and how many vlans on them? Do you have some MST/PVST interaction? Your CPU is definitely too busy but 100s of BPDU per minutes can be just fine on a trunk (50 vlans means 50/2x60 = 1500 BPDUs per minutes).

Regards,

Francois

charles.demers-... Sun, 11/11/2007 - 15:12

Should the trace from my pc to another pc in the vlan and same switch have to by mypc-gatweway-otherpc ?

I wonder why is the gateway in the trace when i'm pinging something on the same switch...

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