[c-nsp] MAC flapping caused ISIS adjacency to go down on ME3600x - How to protect?

[daniel.dib at reaper.nu]

Hi, 

I had a situation where traffic started to loop between two different
EFPs attached to the same bridge domain. There was no split horizon
configured so I could configure that, however if I understand the
documentation correctly I can only have 16 EFPs in same split horizon
group on ME3600x? 

When the loop started there were messages logged about MAC flapping, the
CPU spiked and ISIS adjacency went down and as a consequence also BGP
since loopbacks were no longer reachable. Would split horizon have
protected against this situation? 

Why would the CPU spike due to this? Is there no protection of the
control plane? The documentation talks about some default CoPP policy
but I could not see if it was applied. 

What else can be done to protect against these kind of situations? 

Best regards, 

Daniel Dib 

CCIE #37149