From: Curtis Phillips (cphillips@xxxxxxxxxx)
Date: Sun Jun 16 2002 - 18:20:41 GMT-3
Nigel,
I see your point. I guess the initial confusion was that the poster implied
because a next hop was reachable then the sync issue could be avoided,
rather than that target route (150) needed to be in the IBGP senders routing
table
to reach to two isolated routers.
To be honest the topology is not extremely clear to me from the initial
drawing.
Ascii art leaves alot to be deisred..:-)
thoughts?
Curtis
----- Original Message -----
From: "Nigel Taylor" <nigel_taylor@hotmail.com>
To: <cphillips@suscom.net>; <ccielab@groupstudy.com>
Sent: Sunday, June 16, 2002 12:29 PM
Subject: Re: BGP w/ no synchronization
> Curtis,
>
> I mention using the "next-hop-self" option when trying to achieve
> "BGP" specific reachability. I said BGP specific reachability because
> with the extended ping, as long as the neighboring router(in this case
> RTB and RTD) has known path to the destination(RTA
> -150.150.150.0/24) then technically RTC and RTE, should be able get to
> the 150.150.150.0/24 using the connected interface of RTC-RTB and
> RTD-RTE. Now since the sub-ASs are running the IGP, which is inturn
> redistributed into BGP on RTB, RTA should be able to route to the links
> between both RTB-RTC and RTD-RTE.
>
> Thoughts...
>
> Nigel
>
>
>
> >From: "Curtis Phillips" >Reply-To: "Curtis Phillips" >To: "Nigel Taylor"
> , >Subject: Re: BGP w/ no synchronization >Date: Sun, 16 Jun 2002
> 10:28:08 -0400 > >I think Nigel is right. 150.150.150.0 never was in the
> IGP. Since that is >so, then there can never be synchronization. >Also,
> notice RTC and RTE are the only routers sharing a sub-as and thus
> >relying on IBGP within the sub-as. All routers connected via EBGP will
> of >course >have no sync problems. > >I do not think next-hop will
> resolve any of these issues however. It does >not address the lack of the
> 150 route in the routing able. > >Curtis > > > >----- Original Message
> ----- >From: "Nigel Taylor" >To: >Sent: Sunday, June 16, 2002 8:50 AM
> >Subject: Re: BGP w/ no synchronization > > > > Nick, > > I almost read
> this the way I think you did.. I don't believe that > > the
> 150.150.150.0/24 network on RTA > > was ever a part of any IGP since Hunt
> mentioned that it is injected into >BGP > > with the use of the "network"
> command. > > Since this is the case and only RTB, C, D, and E are running
> the IGP I >don't > > see how the OSPF/BGP route ID could > > be an issue.
> > > http://www.ietf.org/rfc/rfc1403.txt > > > > The problem here is that
> although OSPF is being redistributed into BGP on > > RTB and not
> vice-versa, the 150.150.150.0/24 > > network is never a part of the IGP,
> hence RTC's and RTE's inability to > > become synchronized. Another
> option just thinking > > about it maybe be to have both RTB and RTD
> propagate the route to their >iBGP > > peers with the "next-hop-self" bgp
> command > > and using the "update-source" command to establish the TCP
> peering > > connection. > > . > > Anyone care to comment... :-> > > > >
> HTH > > > > Nigel > > > > > > ----- Original Message ----- > > From:
> "Nick Shah" > > To: "Hunt Lee" ; > > Sent: Sunday, June 16, 2002 7:54 AM
> > > Subject: Re: BGP w/ no synchronization > > > > > > > Dude, > > > > >
> > Here's a hint... > > > > > >
> http://www.cisco.com/warp/customer/459/25.shtml > > > > > > OSPF/BGP
> router - id :) (Check out my post a couple of weeks ago) > > > > > > rgds
> > > > Nick > > > ----- Original Message ----- > > > From: Hunt Lee > > >
> To: > > > Sent: Sunday, June 16, 2002 9:05 PM > > > Subject: BGP w/ no
> synchronization > > > > > > > > > > Okay folks, starting off some late
> nite studying and just noticed > > > something > > > > weird. Got a
> Confederation setup like: > > > > > > > > 150.150.150.0/24---RTA ---RTB
> ---RTD---RTF > > > > | | > > > > RTC RTE > > > > > > > > RTA, B, C, D, &
> E are in a Confederation called AS 1, in which:- > > > > > > > > RTA is
> sub-AS 65530 > > > > RTB & RTC are both in sub-AS 65531 > > > > RTD & RTE
> are both in sub-AS 65532 > > > > > > > > RTF is in AS 2 > > > > > > > >
> RTB, C, D & E are running OSPF as IGP. And OSPF is being >redistributed >
> > > into > > > > BGP at RTB. > > > > > > > > The network 150.150.150.0/24
> is being advertised into BGP by BGP > > "network" > > > > command on RTA.
> > > > > > > > > Ok, here is the thing. The 150.150.150.0/24 network is
> being seen by > > RTA, > > > RTB, > > > > RTD, & RTF. I could ping
> 150.150.150.1 from these four routers. > > However, > > > it > > > >
> can't be seen by RTC & RTE (shown as follows). But when I put "no > > > >
> synchronization" on the middle four routers (RTB, RTC, RTD, & RTE), >then
> > > > > everything becomes fine again... I thought since I used IGP
> (OSPF), > > and > > > if > > > > the router can see the EBGP Next-Hop
> (193.16.0.2) in their routing > > table, > > > then > > > > the synch.
> rule shouldn't apply anymore. > > > > > > > > Am I missing something
> here? > > > > > > > > RouterC#sh ip bgp > > > > BGP table version is 4,
> local router ID is 172.16.0.2 > > > > Status codes: s suppressed, d
> damped, h history, * valid, > best, i - > > > internal > > > > Origin
> codes: i - IGP, e - EGP, ? - incomplete > > > > > > > > Network Next Hop
> Metric LocPrf Weight Path > > > > * i150.150.150.0/24 193.16.0.2 0 100 0
> (65530) i > > > > <-----193.16.0.2 is the Serial int of RTA > > > > > > >
> > *>i172.16.0.0/30 172.16.0.1 0 100 0 ? > > > > * i172.16.0.12/30
> 172.16.0.18 30 100 0 ? > > > > *>i172.16.0.16/30 172.16.0.1 0 100 0 ? > >
> > > *>i193.16.0.0/30 172.16.0.1 0 100 0 ? > > > > * i193.16.0.8/30
> 172.16.0.18 0 100 0 (65532) i > > > > RouterC#sh ip route > > > > Codes:
> C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - >BGP > > >
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area > > > >
> N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 > > > > E1
> - OSPF external type 1, E2 - OSPF external type 2, E - EGP > > > > i -
> IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - >candidate > > >
> default > > > > U - per-user static route, o - ODR > > > > > > > >
> Gateway of last resort is not set > > > > > > > > 172.16.0.0/30 is
> subnetted, 3 subnets > > > > O 172.16.0.16 [110/128] via 172.16.0.1,
> 01:35:04, Serial1 > > > > O 172.16.0.12 [110/192] via 172.16.0.1,
> 01:35:04, Serial1 > > > > C 172.16.0.0 is directly connected, Serial1 > >
> > > 193.16.0.0/30 is subnetted, 1 subnets > > > > O 193.16.0.0 [110/74]
> via 172.16.0.1, 01:35:04, Serial1 > > > > RouterC# > > > > RouterC#ping
> 193.16.0.2 > > > > > > > > Type escape sequence to abort. > > > > Sending
> 5, 100-byte ICMP Echos to 193.16.0.2, timeout is 2 seconds: > > > > !!!!!
> > > > > Success rate is 100 percent (5/5), round-trip min/avg/max =
> 28/32/36 >ms > > > > RouterC# > > > > > > > > > > > > Thanks all! > > > >
> > > > > Hunt > > > > > > > > http://www.sold.com.au - SOLD.com.au > > > >
> - Find yourself a bargain! > > > >
This archive was generated by hypermail 2.1.4 : Tue Jul 02 2002 - 08:12:34 GMT-3