Cisco Systems 3750 manual 121

Chapter 3 Message and Recovery Procedures

SPANTREE Messages

Error Message SPANTREE-2-LOOPGUARD_CONFIG_CHANGE: Loop guard [chars] on port [chars] on [chars].

Explanation The spanning-tree loopguard configuration for the listed interface has been changed. If enabled, the interface is placed into the blocking state. It is marked as loopguard-inconsistent when the message-age timer expires because no BPDUs were received from the designated bridge. This feature is mainly used to detect unidirectional links. The first [chars] is the loopguard state (enable or disable), the second [chars] is the interface name, and the third [chars] is the spanning-tree instance.

Recommended Action Verify that this is the desired configuration for the listed interface. Correct it if this is not the desired configuration; otherwise, no further action is required.

Error Message SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port [chars] on [chars].

Explanation The listed interface has received a BPDU, and therefore, if the inconsistency was caused by a unidirectional link failure, the problem no longer exists. The loopguard-inconsistency is cleared for the interface, which is taken out of the blocking state, if appropriate. The first [chars] is the port name, and the second [chars] is the spanning-tree mode displayed in the show spanning-treeprivileged EXEC command.

Recommended Action No action is required.

Error Message SPANTREE-2-PVSTSIM_FAIL: Blocking [chars] port [chars]: Inconsistent [chars] PVST BPDU received on VLAN [dec], claiming root [dec]:[enet]

Explanation The specified port on the MST switch is blocked. When a designated port on an MST switch is connected to a PVST+ switch, the CIST (MST00) information on the port of the MST switch must be consistently superior (lower bridge ID, lower path cost, and so forth) to the information in all the PVST+ messages. If the port is the root, the CIST (MST00) information on the MST switch must be consistently inferior to all the PVST+ messages. If this constraint is violated, the port on the MST switch is blocked to prevent a potential bridging loop. The first [chars] is the MST switch, the second [chars] is the port, and the third [chars] is the PVST+ switch. The first [dec] is the VLAN ID, the second [dec] is the MST switch, and [enet] is the MST-switch MAC address.

Recommended Action When STP is converging after a new switch or switch port is added to the topology, this condition might happen briefly. In such cases, the port unblocks automatically. If the port remains blocked, identify the root bridge as reported in the message, and configure the appropriate priority for the VLAN spanning tree, consistent with the CIST role on the port of the MST switch.

There could be additional inconsistencies not shown in the message, and the port does not recover until all these are cleared. To determine which other VLANs have inconsistencies, disable and re-enable the port. This message appears again and specifies another VLAN with inconsistencies to be fixed. Repeat this process until all inconsistencies on all VLANs are cleared.

	Catalyst 3750, 3560, 3550, 2975, 2970, and 2960 Switch System Message Guide
OL-8551-04		3-121