Loopguard issue.

[james.reeves]

I have a switch port that goes into a blocking state after the upstream switch is rebooted.  I have to bounce the root port to get it in forwarding.  Loopguard is on globally.  Any ideas?    

  %SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port

!
spanning-tree mode pvst
spanning-tree loopguard default
spanning-tree extend system-id

interface GigabitEthernet
description
switchport access
switchport mode access
end

[lgijssel]

This situation may occur as a result of the changing topology because the rebooted switch stops sending bpdu's.

Please check the document below and verify it's applicability to your scenario.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a0080094640.shtml#loop_guard

regards,

Leo

[letsgomets]

I don't think the problem is with the switch that is doing the loop guard. I

think the problem is with the connected device that you are rebooting. When you reboot it is re-initializing the

the port and spanning tree topology. Perhaps that switch is configured incorrectly. Can you send the config from the connected switch?

You can also automatically recover the connection if you want with.

errdisable recovery interval 400

You may want to understand why this is happening first.

[james.reeves]

It makes it a little tougher b/c I don't mange the other switch.  I just don't quite understand why the port stays in a blocking state after the port comes back up.  Would it be easier to configure my port with portfast or bpduguard to resolve the issue?

Thank you for your assistance!

[lgijssel]

Bpduguard is typically NOT configured on uplink ports because you will always have bpdu's there.

It will result in having the port in err-disabled state.

Portfast can be used but it is not recommended and it does not really improve anything.

If you want to configure something on it, perhaps udld is the best option.

http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_14_ea1/configuration/guide/swudld.html

regards,

Leo