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" > To: "W. Alan Robertson" > Cc: "Peter van Oene" ; "Groupstudy - CCIELAB" > ; "Groupstudy - Cisco Certification" > > 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 selected routes learned via iBPG from r5, and withdrawn 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" > > > To: "W. Alan Robertson" > > > Cc: "Peter van Oene" ; "Groupstudy - CCIELAB" > > > ; "Groupstudy - Cisco Certification" > > > > > > 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 ] > > > > > | | > > > > > | | > > > > > _|___________|_ > > > > > > > > > > > > > > > Originate a route (say the 10.0.0.0/8 route) in AS 1, and see > what > > > > > happens in AS 4. > > > > > > > > > > You should see two entries for the 10/8 network in 'show ip > bgp' > > > > > output, one of which is learned via the eBGP peer, and gets > > > installed > > > > > in your routing table, and the second, learned via the iBGP > peer, > > > > > which does not get installed in your routing table. > > > > > > > > > > That is the time-honored behavior, the behavior we've all come > to > > > know > > > > > and love since the dawn of time, etc, etc, amen. :) > > > > > > > > > > Now, in 12.0(20), this behavior is changed to they behavior I > have > > > > > described in this thread. I don't know when this change > occurred, > > > but > > > > > hope to have that question answered tomorrow. Most of my > other > > > BGP > > > > > customers are running 12.1 stuff... > _________________________________________________________________ > CCIE Security list: http://www.groupstudy.com/list/security.html Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38600&t=38600 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
