On Nov 1, 2011, at 4:57 AM, Nick Hilliard wrote:
> this can be caused by routing loops which happen because the RIB gets out
> of date with respect to the rest of the network.  This will result in lots
> of icmp ttl-expired packets to be generated by the RP, which will cause IP
> Input to get excited.  Try configuring the following:
> 
> mls rate-limit all ttl-failure <xxx>
> mls rate-limit all mtu-failure <xxx>
> mls rate-limit unicast ip icmp redirect <xxx>
> mls rate-limit unicast ip icmp unreachable <xxx>
> 
> If you already have lots of other mls rate limiters configured, you may
> need to be careful when configuring these, because there are more mls rate
> limiter options than the hardware is capable of supporting at the same time.

Thanks for the commands.  Have you seen this shortcoming particularly with the 
RSP720?  My experience is that the SUP720s are getting pretty tired CPU-wise, 
but seemed that after upgrading to RSPs they have a somewhat more "legs", so to 
speak.  Is it simply too much to expect that these processors handle a fairly 
large bgp reset without falling apart?  As I mentioned before, am pretty 
certain this wasn't happening with SRC code, and about the only thing 
feature-wise I've added since then is some HSRP groups.

One thing I did notice since starting this thread is that my bgp fall-over 
command needed some work.  While the core router was correctly dropping the 
lost bgp routes immediately on link down, the other IBGP routers were not, 
presumably because they still had a route to the now down neighbor via a less 
specific backbone aggregate.  So they were waiting on BGP keepalives to fail, 
and I presume still forwarding packets down the invalid path for a while.  
Using "neighbor .. fall-over route-map meh" and matching on the IGP source of 
the IBGP neighbor /32 address should fix it, and get the rest of the IBGP 
neighbors to start re-converging sooner.  Should that help the IP Input settle 
down?

Anyone have recommendations for current decent IOS version for SR train?

Thanks again




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