logging spanning tree changes

[lcaruso]

Hi,

On a 3750 running 12.2(55), what are the logging commands I can use to capture spanning tree changes?

I have a 3750 that is showing me a blocked port one minuted and then later on it is gone and comes back again, but nothing is in the log.

Also, if someone could share recommend commands for switch logging setup?

Thanks.

[Eugene Lau · Accepted solution]

Hi,

You can use

#debug spanning-tree event

Ensure you have your time stamps, plenty of logging buffer and/or a syslog server configured

Reference to config guide:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_55_se/configuration/guide/swlog.html

a. service timestamp

b. logging trap -> debugging level

c. eg. logging buff 100000

Caveats come with debugging - be aware of resources such as CPU and memory, especially if there's a lot of conditions occuring in the network.

spanning-tree event shouldn't be to heavy.

If you are also monitoring from a telnet session to verify the debug --> #term mon

disabling

#undebug all

#term no mon.

Note: As good practice, When troubleshooting STP, ensure that all your "host ports" are portfast enabled. This ensures you do not get any false positives when looking for TCN's in the network.

HTH

Eugene

[lcaruso]

Thanks!