Description

A member link re-joins an AE (Aggregate) bundle causes packets loss.

Symptoms

AE bundle has packet loss, and the router keeps receiving kernel messages "bundle IFL state changed to UP" persistently:

Mar 14 22:24:30 re0-lab /kernel: bundle ae8.0: bundle IFL state changed to UP
Mar 14 22:24:32 re0-lab /kernel: bundle ae8.0: bundle IFL state changed to UP
Mar 14 22:31:10 re0-lab /kernel: bundle ae8.0: bundle IFL state changed to UP
Mar 14 22:31:12 re0-lab /kernel: bundle ae8.0: bundle IFL state changed to UP
This message " kernel: bundle ae8.0: bundle IFL state changed to UP " will be reported whenever a member link re-joins an AE bundle. Member link should transmit LACP packets every second to keepalive by default. If passive side of this link cannot receive a LACP packet within the expire timer, this link will be removed from the AE bundle (LACP packets could be dropped on the link, or intra-chassis). When the passive side receives LACP packets again,  this link will re-join the AE bundle and the above kernel message will be reported.

Solution

Usually LACP packet drop is caused by a physical layer problem.  Use the command " show interface XXX extensive " to check whether there are input errors in the member interface. When finding massive and an increasing number of input errors in a member interface, check transmission/SFP/PIC to help fix the problem.