Message "output packet too big" and then two interfaces goes down.

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Oct 2nd, 2008
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There is router that I saw a few times in the log the message "Output packet size of 1504 bytes too big", just after it two interfaces goes down. The IOS version is 12.2(25). Is it a hardware problem or it would be better to update the IOS version first?


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Giuseppe Larosa Thu, 10/02/2008 - 22:59
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Hello Luiz,


"Output packet size of 1504 bytes too big"


you have an interface with MTU 1500 and a bigger packet should be sent out of it.


Are you deploying MPLS ?


An ip packet of 1500 byte + 4 byte MPLS header makes a 1504 byte PDU that cannot be handled without increasing the MTU.

I've seen this message when deploying MPLS in a network.


depending on the IOS version and platform you could be able to increase the interface MTU or not


try

int fx/y

mtu 1508


I agree the ports shouldn't go down and so I would start to consider an IOS upgrade


Hope to help

Giuseppe


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