From: jonatale@xxxxxxxxxxxxx
Date: Sun Mar 17 2002 - 14:46:43 GMT-3
Folks,
I am very interested in the conclusion of this thread, but I do not have the
time to decipher it. Could somebody please summarize.
W. Alan Robertson wrote:
> Well, that's exactly what I'm seeing, but it certainly wasn't what I
> expected. Nor did it appear to be what our TAC engineer expected...
> I'm going to get the case notes in the morning, and I'll share them
> with the list.
>
> Thanks for mocking this up Przemek... Now if you can manage to get
> that config time down to 20 minutes, instead of an hour, you're going
> to kick butt in the Lab. ;)
>
> ----- Original Message -----
> From: "Przemyslaw Karwasiecki" <karwas@ifxcorp.com>
> To: "W. Alan Robertson" <warobertson@earthlink.net>
> Cc: "Peter van Oene" <pvo@usermail.com>; "Groupstudy - CCIELAB"
> <ccielab@groupstudy.com>; "Groupstudy - Cisco Certification"
> <cisco@groupstudy.com>
> Sent: Tuesday, February 05, 2002 10:50 PM
> Subject: Re: Undocumented iBGP Behavior (Confirmed by Cisco)
>
> > I have prepended it in the router in AS3.
> >
> > I wanted to simulate longer paths from one of the ASes,
> > like it happens between AS1 and AS 701 in reality.
> >
> > Main point I wanted to prove is that initialy both routers
> > have all routes, but after BGP converged, righ router (r6)
> > selected routes learned via iBPG from r5, and withdrawn
> > routes via AS3 from its advertisments to left router (r5).
> >
> > Przemek
> >
> >
> > On Tue, 2002-02-05 at 22:40, W. Alan Robertson wrote:
> > > How are you ending up with a greater number of AS hops for the
> route
> > > on R6 learned via AS3?
> > >
> > > > r6#sh ip bgp 10.0.0.0
> > > > BGP routing table entry for 10.0.0.0/8, version 3
> > > > Paths: (2 available, best #2, table Default-IP-Routing-Table)
> > > > Advertised to non peer-group peers:
> > > > 1.1.34.3
> > > > 3 3 1
> > > ^^^
> > > | Why does there seem to be an as-prepend here? --Alan
> > >
> > > > 1.1.34.3 from 1.1.34.3 (1.1.34.3)
> > > > Origin IGP, localpref 100, valid, external
> > > > 2 1
> > > > 1.1.24.2 from 2.2.2.1 (2.2.2.1)
> > > > Origin IGP, localpref 100, valid, internal, best
> > >
> > > Again, in this case, the iBGP learned route is preferred because
> it is
> > > only two AS hops away... The externally learned route, from peer
> > > 1.1.34.3, shows AS3 twice in the path, making this route 3 AS hops
> > > away.
> > >
> > >
> > > ----- Original Message -----
> > > From: "Przemyslaw Karwasiecki" <karwas@ifxcorp.com>
> > > To: "W. Alan Robertson" <warobertson@earthlink.net>
> > > Cc: "Peter van Oene" <pvo@usermail.com>; "Groupstudy - CCIELAB"
> > > <ccielab@groupstudy.com>; "Groupstudy - Cisco Certification"
> > > <cisco@groupstudy.com>
> > > Sent: Tuesday, February 05, 2002 10:15 PM
> > > Subject: Re: Undocumented iBGP Behavior (Confirmed by Cisco)
> > >
> > >
> > > > Ok,
> > > >
> > > > Lab is done. I expected 20 minutes, it tooks 1 hour.
> > > > Important lesson about time management learnt :)
> > > >
> > > > small legend:
> > > > r5 and r6 are routers in AS4
> > > >
> > > > If anyone care I can send complete configs.
> > > >
> > > > Przemek
> > > >
> > > > r5#sh ip bgp summ
> > > > BGP router identifier 2.2.2.1, local AS number 4
> > > > BGP table version is 2, main routing table version 2
> > > > 1 network entries and 1 paths using 133 bytes of memory
> > > > 1 BGP path attribute entries using 60 bytes of memory
> > > > 1 BGP AS-PATH entries using 24 bytes of memory
> > > > 0 BGP route-map cache entries using 0 bytes of memory
> > > > 0 BGP filter-list cache entries using 0 bytes of memory
> > > > BGP activity 1/9 prefixes, 2/1 paths, scan interval 60 secs
> > > >
> > > > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ
> Up/Down
> > > State/PfxRcd
> > > > 1.1.24.2 4 2 23 22 2 0 0
> 00:18:14
> > > 1
> > > > 2.2.2.2 4 4 27 26 2 0 0
> 00:21:53
> > > 0
> > > > r5#sh ip bgp 10.0.0.0
> > > > BGP routing table entry for 10.0.0.0/8, version 2
> > > > Paths: (1 available, best #1, table Default-IP-Routing-Table)
> > > > Advertised to non peer-group peers:
> > > > 2.2.2.2
> > > > 2 1
> > > > 1.1.24.2 from 1.1.24.2 (1.1.1.1)
> > > > Origin IGP, localpref 100, valid, external, best
> > > > r5#
> > > > telnet-server#6
> > > > [Resuming connection 6 to r6 ... ]
> > > >
> > > > r6#sh ip bgp summ
> > > > BGP router identifier 2.2.2.2, local AS number 4
> > > > BGP table version is 3, main routing table version 3
> > > > 1 network entries and 2 paths using 169 bytes of memory
> > > > 2 BGP path attribute entries using 120 bytes of memory
> > > > 2 BGP AS-PATH entries using 48 bytes of memory
> > > > 0 BGP route-map cache entries using 0 bytes of memory
> > > > 0 BGP filter-list cache entries using 0 bytes of memory
> > > > BGP activity 1/6 prefixes, 2/0 paths, scan interval 60 secs
> > > >
> > > > Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ
> Up/Down
> > > State/PfxRcd
> > > > 1.1.34.3 4 3 21 20 3 0 0
> 00:15:20
> > > 1
> > > > 2.2.2.1 4 4 27 28 3 0 0
> 00:22:13
> > > 1
> > > > r6#sh ip bgp 10.0.0.0
> > > > BGP routing table entry for 10.0.0.0/8, version 3
> > > > Paths: (2 available, best #2, table Default-IP-Routing-Table)
> > > > Advertised to non peer-group peers:
> > > > 1.1.34.3
> > > > 3 3 1
> > > > 1.1.34.3 from 1.1.34.3 (1.1.34.3)
> > > > Origin IGP, localpref 100, valid, external
> > > > 2 1
> > > > 1.1.24.2 from 2.2.2.1 (2.2.2.1)
> > > > Origin IGP, localpref 100, valid, internal, best
> > > > r6#
> > > >
> > > >
> > > > Once better route is selected in Local-RIB, the other,
> > > > previously advertised is withdrawn.
> > > >
> > > >
> > > >
> > > > On Tue, 2002-02-05 at 21:15, W. Alan Robertson wrote:
> > > >
> > > > > If you can, build your test scenario to look like this:
> > > > >
> > > > >
> > > > > [eBGP ]
> > > > > ___[AS 1]___
> > > > > | |
> > > > > | |
> > > > > [ eBGP ] [ eBGP ]
> > > > > [ AS 2 ] [ AS 3 ]
> > > > > | |
> > > > > | |
> > > > > | |
> > > > > | |
> > > > > [ BGP ] [ BGP ]
> > > > > [ AS 4 ] [ AS 4 ]
> > > > > | |
> > > > > | |
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