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Community Member

MTU error message

I have a CAT6509 with MPLS.. two redundant MSFC2 blades. Whenever I go in to configure one of the MSFC's I get the message:

%MROUTE-4-MTU_MISMATCH : WARNING: With IP multicast enabled, interfaces which transmit traffic from larger to smaller MTU interfaces may not be hardware switched due to fragmentation. A degradation in performance may occur.

According to Cisco:

Explanation This warning message provides information about transmitting traffic from larger to smaller MTU interfaces.

Recommended Action Set MTU values on all interfaces to be identical to avoid fragmentation.

I am not sure what to do about this because I do not see any specific MTU settings. Can someone help me with this?

- Bill E.

3 REPLIES
Community Member

Re: MTU error message

you need to check the mroute table.

Check the oil list.Foreach oil check the MTU with "shwo ip int " command.That should give a clue to you.

Community Member

Re: MTU error message

Thank you for your posting. I did as you recommended and all interfaces are set to MTU of 1500 - the default I believe. Any other thoughts?

- Bill

Community Member

Re: MTU error message

I contacted Cisco directly and it turns out this is a "debug" type message and I do not have to worry about it. Just an FYI for anyone who reads this.

- Bill

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