[c-nsp] BGP convergence in VRF vs. global routing table on 7600router

[Rodney Dunn]

The bug I was referencing is:

CSCek71050 
CPU Utilization at 100% in BGP Router process in 12.2(33)SRB1

fixed in SRB2.

Rodney

On Fri, Oct 19, 2007 at 08:42:27AM -0400, Rodney Dunn wrote:
> Can you try SRB2?
> 
> On Fri, Oct 19, 2007 at 02:31:03PM +0200, Christian Bering wrote:
> > >From: Oliver Boehmer (oboehmer) [mailto:oboehmer at cisco.com] 
> > 
> > Hi Oliver,
> > 
> > >Can you pls describe which "convergence" you are referring? Time it
> > >takes after bringing up the session until every other PE has 
> > >the routes?
> > >Or the table version on the CE and the receiving PE is the same?
> > 
> > Time it takes for PE1's CPU to fall back to normal utilisation and all
> > destinations reachable again after PE2 loses an upstream provider.
> > 
> > Given that PE1 is a "normal" PE terminating customers and PE2 a border
> > router-like PE terminating an upstream provider.
> > 
> > >If you talk about a distant PE receiving the full table from the RR via
> > >iBGP, the overhead will likely depend on the RD setup. I assume you use
> > >a common RD for the "internet" VRF on all your PEs, right? 
> > 
> > Correct.
> > 
> > And the RRs (7301s) take very little time to converge. After a minute or
> > so, the BGP process has fallen to normal levels. The CPUs in SUP720s
> > aren't overly fast - I am aware of that.
> > 
> > >This could be one reason. CEs advertising > 200k prefixes are 
> > >not widely seen in 2547bis environments :-)
> > 
> > I know. :-/  It's somewhat of a shame because on a sheet of paper, it
> > seems like a good approach. In reality, it's not widely used and doesn't
> > seem to get tested well or have the code optimised for it.
> > 
> > >next to PMTUD, none I could think of without knowing more details.
> > 
> > Already done.
> >  
> > >>Any improvements to this behaviour in SRB2 over SXE, SXF or SRA?
> > 
> > >need to know more details..
> > 
> > Alright; hope I supplied them. :)
> > 
> > >From: Rodney Dunn [mailto:rodunn at cisco.com] 
> > 
> > Hi Rodney,
> > 
> > >I need to check this in the lab but if you look at the vpn table are
> > >we not allocating a VPNV4 label for each prefix when it's in the
> > >VRF?
> > 
> > On PE2 ("border router"), there's an "in label" for every prefix, yes.
> > No "out label" for locally learned prefixes (from upstreams).
> > 
> > On PE1 ("normal" PE), there's an "out label" for all prefixes learned
> > from PE2 and other "border routers". "in label" for locally terminated
> > prefixes.
> > 
> > As I wrote initially, it's only the BGP process that chews up CPU during
> > convergence on PE1 and other "normal" PEs.
> > 
> > -- 
> > Regards
> >  Christian Bering
> >  IP engineer, nianet a/s
> >  Phone: (+45) 7020 8730
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