[c-nsp] 6500 SXD7b VRRP issue

[Kevin Loch]

Jon Lewis wrote:
> I just searched bug toolkit and didn't see anything similar, but has 
> anyone else had issues with VRRP "freaking out" with 6500s running 
> s72033-pk9sv-mz.122-18.SXD7b.bin?
> 
> Last night, we lost connectivity to one of our BGP providers.  10 
> seconds after the
> 
>  %BGP-5-ADJCHANGE: neighbor x.x.x.x Down BGP Notification sent
>  %BGP-3-NOTIFICATION: sent to neighbor x.x.x.x 4/0 (hold time expired) 0 
> bytes
> 
> all the interfaces on this router running VRRP started having their 
> states change from backup to master to backup every few seconds.  After 
> about 40 seconds of this, it settled down and all the VRRP states went 
> back to their original state.  While this was going on, the other 6500 
> participating in the VRRPs (which was the master) logged nothing and 
> thought it was the master the whole time.

This is likely a side effect of the cpu being maxed out, or encountering
control plane rate limiting.  Was there something that spiked the cpu
or exeeded your control plane limits that caused both the BGP session to
drop and the vrrp flaps?  Loops on the switch that include cpu affecting
packets (like vrrp for example) can easily do this.

It is also possible that just importing a full table (which maxes out
the cpu for a minute) caused the vrrp flaps as a side effect.

Do you have the control-plane policer configured with a low rate limit
and are there exceptions for BGP and vrrp?

- Kevin