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MLS-4-RESUMESC:Resume MLS after detecting too many moves

We have a Catalyst 5513 with 5.5(7)code

that is a core switch for 40 distribution switches that are a mix

of 5000's and 2900's. This core switch

has been logging '%MLS-4-RESUMESC:Resume MLS after detecting too many moves' about every hour for the

past few weeks. Any hints for troubleshooting this problem that doesn't involve going from closet to closet looking for hubs or other devices that could cause a loop?


Re: MLS-4-RESUMESC:Resume MLS after detecting too many moves

These syslog messages indicate that the switch is relearning one or more MAC addresses on multiple ports in rapid succession. For example, on an access switch with two uplinks to the core of the network, the switch might learn a given MAC address first on one uplink and then on the other very rapidly.

If you see these messages infrequently, it is most likely a transitory Layer 2 (spanning-tree) loop, resulting in packet flooding in one or more VLANs.

If you are seeing an excessive number of these messages (for example, if your syslog server log file or your switch console are being flooded with these messages), the problem might be due to:

A permanent Layer 2 (spanning-tree) loop

One or more faulty switch ports

A bad cable (for example, a unidirectional fiber link)

Other bad hardware (not necessarily on the switch generating the messages)

Misconfigured device (for example, a traffic generator sending traffic to two switch ports using the same MAC address)

If you are confident there is no Layer 2 loop or faulty hardware, you are not using MLS on the switch, and you want to eliminate these messages, you can disable MLS on the switch (with the set mls disable command). Alternately, you can modify the logging level for the "MLS" facility to 3 or lower using the command set logging level mls 3 default. However, these solutions simply mask the problem.

In addition to the suggestions above, consider upgrading the switch software to the latest maintenance release for your software release train, which integrates several optimizations relating to this problem.

Cisco Employee

Re: MLS-4-RESUMESC:Resume MLS after detecting too many moves

Use this link to troubleshooting: