Re Bruce,
On Wed, Aug 31, 2005 at 05:44:05PM -0700, Bruce Pinsky wrote:
> Andre Beck wrote:
> >
> > I just found that a 72xx running 12.2(25)S5 shows an increased number
> > of active BGP prefixes. Compared to the other iBGP mesh members, the
> > number from "sh ip bgp summary" is way too large:
> >
> > ----------------------------------------------------------------------------
> > BGP router identifier 212.111.224.8, local AS number 15372
> > BGP table version is 12935683, main routing table version 12935683
> > 190844 network entries using 21565372 bytes of memory
> > ^^^^^^^^^^^^^^^^^^^^^^
> > 302705 path entries using 15740660 bytes of memory
> > 57469/31045 BGP path/bestpath attribute entries using 6206652 bytes of memory
> > 51832 BGP AS-PATH entries using 1384316 bytes of memory
> > 1009 BGP community entries using 39244 bytes of memory
> > 0 BGP route-map cache entries using 0 bytes of memory
> > 42054 BGP filter-list cache entries using 504648 bytes of memory
> > BGP using 45440892 total bytes of memory
> > BGP activity 190845/0 prefixes, 4608899/4306191 paths, scan interval 60 secs
> > ^^^^^^
> > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
> > 212.111.224.2 4 15372 84994 3335308 12935678 0 0 8w3d 2
> > 212.111.224.7 4 15372 4116825 3335309 12935678 0 0 8w3d 135105
> > 213.148.131.181 4 20676 6778241 169985 12935683 1 0 8w3d 167596
> > ----------------------------------------------------------------------------
> >
> > Using "sh ip route summary", the real amount of BGP routes comes out
> > at a more reasonable count:
> >
> > Route Source Networks Subnets Overhead Memory (bytes)
> > bgp 15372 110058 59849 10874048 26063524
> > External: 127676 Internal: 42231 Local: 0
>
> Info from "show ip route summary" is displaying the number of BGP routes in
> the forwarding RIB, i.e. installed in the routing table. The output of
> "show ip bgp summary" is showing you the count of the number of network
> entries across all of your BGP peers in the BGP adacency RIB structures.
> That would explain the difference between the counts.
Yep, but up to now, the value in the third line of "sh ip bgp summary" has
always been a somewhat reliable count of the total number of unique BGP
prefixes the box is getting from peers. This all of a sudden changed with
12.2(25)S it seems.
> What versions are running on your other BGP routers that you included? I'd
> be curious to do a quick test to see if I can duplicate your results.
The other box with eBGP runs 12.0(21)S and the pure iBGP one is at
12.2(18)S (with some digit after the S in both cases, of course). The
router in question showed a number more similar to the other boxes before
upgrade to 12.2(25)S, so it's not just a topology glitch. It's also
interesting that this box didn't come up with this number directly after
boot. At this time (and the following days), the prefix count seemed well
in the sane area. That "off by 20000 prefixes" situation developed slowly
and constantly over a month or so, and it seems it's still growing - I'm
at 191424 now. Not that it actually matters as long as memory is plenty
and per-peer prefix limits are not triggered to tear down sessions. But
it hoses my MRTG graphing...
> I know there were changes in 12.2(25)S in several areas of code that
> contribute to the output of "show ip bgp summary". I suppose there could
> be a bug that was introduced as a result of some of those changes.
Either that or the meaning of this value has changed to something I don't
understand. It doesn't seem to be a combination of individual peer contri-
butions and certainly isn't path cumulation (the box got some 300k paths).
So a bug seems likely.
> I'd probably open a case at this point.
It's not that mission critical here, just another counter fun issue. But
if you can replicate it and want to throw it at TAC, all the better ;)
Thanks,
Andre.
--
The _S_anta _C_laus _O_peration
or "how to turn a complete illusion into a neverending money source"
-> Andre Beck +++ ABP-RIPE +++ IBH Prof. Dr. Horn GmbH, Dresden <-