Cisco 6509 debug spanning-tree problem

[svjatoslav]

Hello everyone. Can you help me please, I'm testing debug spanning-tree functions in a lab, hardware is Cisco 6509 with SUP-720-3B and WS-X6748-SFP, IOS is 12.2.33.SXJ. It's a root in some vlan's, stp mode is rapid-pvst.

I wanted to see how spanning-tree is working (STP packets dump, etc.), and entered following commands on 6509:

no logging console

no logging monitor

logging buffered 40960 debugging

logging trap debugging

logging X.X.X.X (IP of syslog-server)

Then, I turned the "debug spanning-tree all" mode on. Now, I expect to see BPDU packets from Cisco, and other spanning tree events in logs on syslog server, or in log buffer, but I don't get anyting there. Except, there're some lines in log (they repeat very rare):

Nov  8 18:13:35 64: 1w5d: SPANTREETYPE: getting tree type vlan for parameter 1 value 0

Nov  8 18:13:35 65: 1w5d: STP CFG: found port cfg GigabitEthernet1/1 (53E91B04)

Nov  8 18:13:35 66: 1w5d: STP CFG: get port param unknown 0 GigabitEthernet1/1 1=2 rc=1

Nov  8 18:13:35 67: 1w5d: STP CFG: found port cfg GigabitEthernet1/1 (53E91B04)

Nov  8 18:13:35 68: 1w5d: STP CFG: get port param unknown 0 GigabitEthernet1/1 1=3 rc=1

Nov  8 18:13:35 69: 1w5d: STP CFG: found port cfg GigabitEthernet1/1 (53E91B04)

Nov  8 18:13:35 70: 1w5d: STP CFG: get port param unknown 0 GigabitEthernet1/1 1=1 rc=1

...skipping...

Nov  9 17:16:58 293: 1w6d: STP CFG: get port param unknown 0 GigabitEthernet1/1 1=2 rc=1

Nov  9 17:16:58 294: 1w6d: STP CFG: found port cfg GigabitEthernet1/1 (53E91B04)

Nov  9 17:16:58 295: 1w6d: STP CFG: get port param unknown 0 GigabitEthernet1/1 1=3 rc=1

Nov  9 17:16:58 296: 1w6d: STP CFG: found port cfg GigabitEthernet1/1 (53E91B04)

What am I doing wrong? Why there's so little info in logs?

[Arumugam Muthaiah · Accepted solution]

Hi,

Many STP debug commands are intended for development engineering use. They do not provide any output that is meaningful to someone without detailed knowledge of the STP implementation in Cisco IOS software. Some debugs can provide output which is instantly readable, such as port state changes, role changes, events such as TCs, and a dump of received and transmitted BPDUs

To see the general events log, issue the debug spanning-tree event command for Per VLAN Spanning-Tree (PVST) and Rapid-PVST. This is the first debug that gives a general idea of what is happening with STP

To see the port STP state changes, issue the debug spanning-tree switch state command together with the debug pm vp command:

cat-sp# debug spanning-tree switch state

Spanning Tree Port state changes debugging is on

cat-sp# debug pm vp

Virtual port events debugging is on
Nov 19 14:03:37: SP:     pm_vp 3/1(333): during state forwarding, got event 4(remove)
Nov 19 14:03:37: SP: @@@ pm_vp 3/1(333):
  forwarding -> notforwarding

port 3/1 (was forwarding) goes down in vlan 333

Note: Use the remote login switch command in order to access the switch console or a specific module and then enter debug spanning-tree events. The debug command also possibly increases the CPU utilization

Refer:

Troubleshooting STP on Catalyst Switches Running Cisco IOS System Software

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080136673.shtml#stp_debug

Regards,

Aru

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[svjatoslav]

Thank you, the remote login switch command solved it. Maybe, It's not really clear in documentation, that I must issue the debugging commands for spanning tree directly on the Switch processor.

[Arumugam Muthaiah]

Hi,

Thanks for your kind response. Yes, when you telnet into a 6500 switch which is running Native IOS, you are automatically brought to the Route Processor (RP) environment.

when you do the remote login switch command helps you login into Switch processor (SP) where you can capture debug spanning-tree relevant activities.

Regards,

Aru

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