From: Nigel Taylor (nigel_taylor@xxxxxxxxxxx)
Date: Sun Jun 16 2002 - 13:29:51 GMT-3
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