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Beginner

STP-2-LOOPGUARD Block and Unblock Vlans on Port-Channel (Nexus-7000)

We recently have this problem happened twice (two days in raw at almost at the same time range). Basically, Nexus 7k block all Vlans from the port-channel to the other 7k, then it unblocked them from the port immidiately or after 2-4  seconds. It flapped several times and then recovered by itself.

The traffic was affected by this. I am just wondering what could cause this problem. There is no possible loop in the network other than the port channel (4 link).

BTW., we upgraded the OS to 5.1.3 and EPLD to 5.1.1 the day this happened the first time.

Logs:

2011 Jun 11 17:13:41 7000-11 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel2 on VLAN0005.

2011 Jun 11 17:13:41 7000-11 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel2 on VLAN0008.

2011 Jun 11 17:13:42 7000-11 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel2 on VLAN0011.

2011 Jun 11 17:13:42 7000-11 %STP-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port port-channel2 on VLAN0005.

2011 Jun 11 17:13:42 7000-11 %STP-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port port-channel2 on VLAN0008.

2011 Jun 11 17:13:42 7000-11 %STP-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port port-channel2 on VLAN0011.

2011 Jun 12 17:14:01 7000-11 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel2 on VLAN0005.

2011 Jun 12 17:14:01 7000-11 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel2 on VLAN0008.

2011 Jun 12 17:14:01 7000-11 %STP-2-LOOPGUARD_BLOCK: Loop guard blocking port port-channel2 on VLAN0011.

2011 Jun 12 17:14:03 7000-11 %STP-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port port-channel2 on VLAN0005.

2011 Jun 12 17:14:03 7000-11 %STP-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port port-channel2 on VLAN0008.

2011 Jun 12 17:14:03 7000-11 %STP-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port port-channel2 on VLAN0011.

Configurations of the port:

interface port-channel2

  description PORT-CHANNEL:7000-12

  switchport

  switchport mode trunk

  spanning-tree port type network

  spanning-tree guard loop

  logging event port link-status

  logging event port trunk-status

  mtu 9216

  storm-control broadcast level 10

Does high CPU usage could cause this problem? Any comments will be great appeciated. Thanks.

2 REPLIES 2
Cisco Employee

STP-2-LOOPGUARD Block and Unblock Vlans on Port-Channel (Nexus-7

Hello Tony,

Which device is STP ROOT for all these vlans ?  the device reporting this error or some other device ?

Do you have vPC feature enabled ? If so, do you have "peer-switch" enabled on vPC peers ?

Yogesh

Highlighted
Beginner

STP-2-LOOPGUARD Block and Unblock Vlans on Port-Channel (Nexus-7

Hi, Yogesh,

Thanks for taking time to review my case. The other one (7k-12) is the STP ROOT for most of Vlans and this 7k (7k-11) reported those error. vPC feature was disabled. Is it possible because of High CPU usage causing this problem because there was spike during that period.

Thanks,

Tony

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