[c-nsp] blackholed traffic on ether-channel

[Nathan Lannine]

>
> Setup:
> 4 port LACP channel, C6880 <->  Nexus 7k
>
> Recently we had the issue that most (not all) traffic was black-holed on a
> C6880.
> No interface counters, nor the port-channel status, nor an NMS pointed to
> any abnormal behavior.
>
> Finally, the problem was resolved by shutting down a specific  interface on
> C6880.
> It seems that one defect port affected the function of the entire
> port-channel !!
>
> Have you ever encountered a similar issue ?

We encountered a similar issue as part of bug ID CSCut40421 specific
to 10G links.  There was a somewhat complex workaround, but we
upgraded to resolve it.  I think the bug was a regression in
15.1(2)SY5 from a prior fix to resolve the same issue with 1G links.
We went to 15.2(1)SY1a, which fixed it for us.

Nathan