Sunday, February 22, 2009

Intermediate spanning tree

We cover intermediate spanning tree concepts. The importance of specifying your root bridge and backup root bridge with spanning-tree priority. Using portfast to allow host ports to start forwarding without waiting for 30 seconds. Using bpduguard to disable portfast-enabled ports where someone erroneously plugs in a switch. Using errdisable timeout to automatically reenable those ports after 15 minutes. Using rootguard to prevent improper switches from becoming your spanning-tree root. The dangers of using bpdufilter to ignore and delete BPDUs. How uplinkfast can enable access switches to failover between uplinks without delay. And using backbone fast to improve responsiveness to indirect link failures by eliminating the need for the 20 second maxage timeout.

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2 Comments:

Blogger Darrell Root said...

Diagram is at http://www.ciscohandsontraining.com/photo/spanning-tree-2.pdf

February 22, 2009 at 8:13 PM  
Blogger Jonas said...

Hi Darrell, just about to try out for my BCMSN exam, and as always your podcast is immensely helpful. Thanks. Just noticed one thing in this episode (that I didn't catch the last time I went through it); you mentioned that bpdu filtering causes the port to discard incoming BPDU's while still sending them. I don't think that's correct; bpdu filtering disables outgoing bpdu's on the port as well.

Again, thank you for a wonderful job, keep it up.

Regards Jonas H

November 5, 2009 at 4:11 PM  

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