[c-nsp] BGP confusion in 12.2(18)SXE2

[Bruce Pinsky]

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Gert Doering wrote:
> Hi,
> 
> I was adventurous (or maybe "stupid") enough to run 12.2(18)SXE on our
> Sup720 based router things.
> 
> Yesterday BGP started acting up in *very* interesting ways ("show ip b su"
> claimed to have seen "50" prefixes from a given peer, while the detailed
> commands, like "show ip b neigh x.x.x.x received-routes" displayed 
> *one* prefix, or just a hand ful).  
> 
> After clearing all neighbours on the box (very nice thing to do on a 
> router that does "core + major peering point") everything seemed to be
> normal, but today I noticed another funny:
> 
> Cisco#sh ip b 4.0.0.0   
> BGP routing table entry for 4.0.0.0/8, version 15607368
> Paths: (5 available, best #2, table Default-IP-Routing-Table)
>         ^^ it says "5" here
> 
>   Advertised to update-groups:
>      3         
>   1273 3356, (aggregated by 3356 4.68.0.8)
>     208.175.XX.YY (metric 172800) from 193.149.XX.YY (193.149.XX.YY)
>       Origin IGP, metric 1, localpref 100, valid, internal, atomic-aggregate
>   1273 3356, (aggregated by 3356 4.68.0.8)
>     62.208.XX.YY (metric 156416) from 193.149.XX.YY (193.149.XX.YY)
>       Origin IGP, metric 1, localpref 100, valid, internal, atomic-aggregate, best
>   13237 6461 3356, (aggregated by 3356 4.68.0.8)
>     217.71.XX.YY from 217.71.XX.YY (80.86.XX.YY)
>       Origin IGP, metric 1, localpref 100, valid, external, atomic-aggregate
> 
> ... and then lists *3* paths.
> 
> This happens for just about any prefix learned from external sources
> (the number of actual paths varies, but it always displays less
> paths than given in the summary line).
> 
> Has anyone of you seen this before?  Is this a known issue in SXE2?
> 
> I *think* this started happening when I changed the "full eBGP feed"
> session connected to this router to "no neighbour 217.71.xx.yy soft in"
> - at least that's when our customers started yelling at us... - but
> I've done this to various routers in the past, and never seen such 
> strange BGP behaviour...
> 
> We're running various 7200s with 12.2(18)S<n>, and these never did 
> funny BGP things - so I'm a bit confused whether 12.2(18)SXE2 has the
> same BGP code, or maybe something completely different?
> 

Andre Beck reported some similar prefix counting issues in 12.2(25)S on
7200's.  He indicated that the total networks reported in "show ip bgp sum"
was higher than he would expect.

Rodney suspects CSCeh16989 which has a fix in 12.2(30)S (no 6500 or 7200
image on that release), but I don't see a fix yet for 12.2SX.

That bug seems to have been introduced by a fix that would have been
integrated into 12.2(18)SXE and hence you would not have seen it in
12.2(18)SXD, SXB, etc.

The bug also claims to continually increase memory consumption, so you may
want to watch that for both 1) signs that this is the problem you are
encountering; 2) operationally impacting memory exhaustion.

If you don't need what's in that version, you may want to consider going
back to your previous image until this issue is resolved.

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

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