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Chapter 2. Message and Recovery Procedures 33
SPANTREE-2-CHNL_MISCFG: Detected loop due to etherchannel misconfiguration of [chars] [chars]
Explanation This message means that a loop that caused the misconfiguration of a channel group has
been detected. An example of such a misconfiguration would be when the ports on one side of the
EtherChannel either are not configured to be in the channel or failed to bundle for some reason. The other
side has successfully bundled the ports into the EtherChannel.
Response Determine which local ports are involved by using the show interfaces status err-disabled
privileged EXEC command, and then verify EtherChannel configuration on the remote device by using the
show etherchannel summary user EXEC command on the remote device. When the configuration is
corrected, enter shutdown and no shutdown interface configuration commands on the associated port-
channel interface.
SPANTREE-2-LOOPGUARD_BLOCK: Loop guard blocking port [chars] on [chars].
Explanation This message means that the spanning-tree message age timer has expired because no
bridge protocol data units (BPDUs) were received from the designated bridge. Because this condition
could be caused by a unidirectional-link failure, the interface is put into the blocking state and marked as
loop-guard-inconsistent to prevent possible loops from being created. The first [chars] is the name of this
port, and the second [chars] is the spanning-tree mode displayed in the show spanning-tree privileged
EXEC command.
Response Enter the show spanning-tree inconsistentports privileged EXEC command to review the
list of interfaces with loop-guard inconsistencies. Determine why devices connected to the listed ports are
not sending BPDUs. One reason might be that they are not running the Spanning Tree Protocol (STP). If
so, you should disable loop guard on the inconsistent interfaces by using the spanning-tree guard none
interface configuration command or by starting STP on the remote side of the links.
SPANTREE-2-LOOPGUARD_CONFIG_CHANGE: Loop guard [chars] on port [chars] on [chars].
Explanation This message means that the spanning-tree loop-guard configuration for the listed
interface has been changed. If enabled, the interface is placed into the blocking state. It is marked as loop-
guard-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 loop-
guard state (enable or disable), the second [chars] is the interface name, and the third [chars] is the
spanning-tree instance.
Response 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.
SPANTREE-2-LOOPGUARD_UNBLOCK: Loop guard unblocking port [chars] on [chars].
Explanation This message means that 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 loop-guard-
inconsistency is cleared for the interface, which is taken out of the blocking state, if appropriate. The first
[chars] is the name of this port, and the second [chars] is the spanning-tree mode displayed in the show
spanning-tree privileged EXEC command.
Response No action is required.