[c-nsp] Cisco 7301 running at 99% CPU doing iBGP update

[Bruce Pinsky]

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jamie baddeley wrote:
> On Tue, 2006-06-27 at 11:51 -0700, Bruce Pinsky wrote:
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>> Rodney Dunn wrote:
>>> Wonder if he's getting recursive next hops.
>>>
>>> Make sure all your iBGP peers are next hop self.
> 
> Thanks for the thoughts guys.
> 
> Yep, got that as standard in IBGP peer group. And the iBGP peer is
> learning things appropriately (if not somewhat slowly (the update ended
> up taking an hour)) - Next hop is set to the iBGP peer you learn it from
> etc.
> 
> I already had MTU hardset to 9000 on both interfaces. Right now the link
> between the two routers is a 2 metre piece of ethernet cable running at
> 1 gig. No errors being reported. I'll change down to something like 1500
> MTU to see if that makes a difference and turn damned autoneg off (even
> if we do have no errors)
> 
> About the only other thing I should point out is that the International
> Feed is coming via EBGP multihop, and I'm using OSPF to stand up the
> loopbacks in the IGP. But I'd be amazed if they had anything to do with
> it.
> 

You have the MTU set to 9K, but if you don't configure path MTU discovery,
it's still a 576 MSS in TCP.  Check out the MSS in your TCP sessions via a
show command to be sure.  With that small an MSS, it would be easy for the
transmitting interface to overrun the receiver on the other end.  Are sure
that you aren't getting drops on the receiving side?

- --
=========
bep

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