From: Hunt Lee (ciscoforme3@xxxxxxxxxxxx)
Date: Sat Jun 22 2002 - 23:03:24 GMT-3
Thanks for all of you guys help on this one :)
I figured that if I also redistribute BGP back into OSPF at RTB, then
RTC & RTE would now be able to synchronize via the IGP (OSPF).
However, before I try this mutual redistribution at RTB, I also
noticed another thing that I don't understand. I advertised the link
between RTD & RTE (i.e. 172.16.0.12/30) by a network command at RTD,
but RTC just can't see this link (it kept on saying it's not sync),
even though it is reachable via OSPF (the middle 4 routers are
running OSPF).
RouterC#sh ip bgp
BGP table version is 8, 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
*>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 bgp 172.16.0.12/30
BGP routing table entry for 172.16.0.12/30, version 0
Paths: (1 available, no best path)
Not advertised to any peer
Local
172.16.0.18 (metric 128) from 172.16.0.1 (193.16.0.1)
Origin incomplete, metric 30, localpref 100, valid, internal,
not synchronized, ref 2
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, 01:43:32, Serial1
O 172.16.0.12 [110/192] via 172.16.0.1, 01:43:32, Serial1 <--
but it is reachable via OSPF ??
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, 01:43:32, Serial1
RouterC#
Thanks all!
Hunt
From: "Roger Schotsal" <schotsal@hotmail.com>
I took a few minuets to think about your senario. I think it behaves
as
it should.
BGP will not place a route in the table unless the route is in the in
the
IGP - if the route is learned from an iBGP neighbor. Routers B & D
learn
the routers from eBGP neighbors (different confederation ASs).
Router
B
(AS 65531) learns the route from router A (65530) - this is an eBGP
like
session - the route is placed in the routing table & is thus
advertised
to
its neighbors. This same method works to propegate the route to
router
D.
Router B also advertises the route to router C - but since thay are
in
the
same AS - router C does not place the route in the routing table
without a
IGP route to support it.
As you discovered - this can be fixed by disableing synchronization
on
router C & E.
Note - in you config - I did not see an ospf route for
150.150.150.0/24
-
I am assuming you did not add that route to ospf.
thanx,
Roger
http://www.sold.com.au - SOLD.com.au
- Find yourself a bargain!
http://www.sold.com.au - SOLD.com.au
- Find yourself a bargain!
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