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LACP error "received pdu - length mismatch for lacp" received on interface



Article ID: KB17674 KB Last Updated: 04 Mar 2017Version: 2.0

The LACP error listed below was received on an interface that was connected to a server.  The purpose of this KB article is to define this message and consequences.
/kernel: %KERN-3: ge-0/0/1: received pdu - length mismatch for lacp : len 128, pdu 124
Received errors in log indicating LACP pdu mismatch from server connected to this interface. 

Message noted in log file:
/kernel: %KERN-3: ge-0/0/1: received pdu - length mismatch for lacp : len 128, pdu 124
This error message is logged in the /var/log/messages when the EX Switch recieves an LACP frame on existing LAG ports which are more than 128 bytes in length.
According to the LACP specification 802.3ad-2000,  the maximum size of allowed LACP frame is 124 bytes. It states the maximum allowed frame size is 124 bytes + 4 bytes for FCS.So the total allowed frame size is 128bytes including FCS.

To troubleshoot you should provide a packet capture to verify frame size sent from the server or other device.

NOTE: The FCS is added by the underlying MAC layer and regular packet capture softwares remove the FCS and display only the LACP PDU.

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