From: Ouellette, Tim (tim.ouellette@eds.com)
Date: Sat Jan 11 2003 - 01:12:54 GMT-3
I set the scenario up just the same (I love those conditional defaults, btw)
R7=RTA, R1=RTG, R2=RTF
other than that, you can see the picture on page 399 of Halabi.
After my initial setup, without really looking at the routing table or r7
here's what "debug
ip routing" gave me....
r7#
*Feb 28 20:03:38: RT: add 172.16.70.0/30 via 0.0.0.0, connected metric [0/0]
*Feb 28 20:03:38: RT: add 172.16.20.0/30 via 0.0.0.0, connected metric [0/0]
*Feb 28 20:03:38: RT: add 0.0.0.0/0 via 172.16.50.1, bgp metric [200/0]
*Feb 28 20:03:38: RT: default path is now 0.0.0.0 via 172.16.50.1
*Feb 28 20:03:38: RT: new default network 0.0.0.0
*Feb 28 20:03:38: RT: add 193.78.0.0/16 via 172.16.50.1, bgp metric [200/0]
*Feb 28 20:03:38: RT: add 172.16.50.0/30 via 172.16.70.2, ospf metric
[110/128]
*Feb 28 20:03:38: RT: closer admin distance for 0.0.0.0, flushing 1 routes
*Feb 28 20:03:38: RT: add 0.0.0.0/0 via 172.16.70.2, ospf metric [110/1]
*Feb 28 20:03:38: RT:
r7#default path is now 0.0.0.0 via 172.16.70.2
*Feb 28 20:03:38: RT: new default network 0.0.0.0
One would think that after learning a 0.0.0.0/0 route with AD of 200 that a
new route of
0.0.0.0/0 with an AD of 100 would be normal right..... Just to test that I
did the following.
Gateway of last resort is 172.16.70.2 to network 0.0.0.0
172.16.0.0/30 is subnetted, 3 subnets
O 172.16.50.0 [110/128] via 172.16.70.2, 00:03:44, Serial0.17
C 172.16.20.0 is directly connected, Serial1
C 172.16.70.0 is directly connected, Serial0.17
O*E2 0.0.0.0/0 [110/1] via 172.16.70.2, 00:01:59, Serial0.17
B 193.78.0.0/16 [200/0] via 172.16.50.1, 00:02:05
7#conf t
Enter configuration commands, one per line. End with CNTL/Z.
r7(config)#router bgp 3
r7(config-router)#distance bgp 20 109 109
r7(config-router)#
r7#clear ip route *
r7#r
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, ia - IS-IS inter
area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 172.16.50.1 to network 0.0.0.0
172.16.0.0/30 is subnetted, 3 subnets
O 172.16.50.0 [110/128] via 172.16.70.2, 00:00:00, Serial0.17
C 172.16.20.0 is directly connected, Serial1
C 172.16.70.0 is directly connected, Serial0.17
B* 0.0.0.0/0 [109/0] via 172.16.50.1, 00:00:00
B 193.78.0.0/16 [109/0] via 172.16.50.1, 00:00:00
r7#
As soon as I brought the AD of BGP down below 110 (of ospf) then the BGP
router got in the table.
As to be expected. I just wanted to make sure that BGP and OSPF didn't talk
to one another in
some weird fasion to negotiate who gets in the routing table.
r1#r
Gateway of last resort is 172.16.50.1 to network 0.0.0.0
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
172.16.0.0/30 is subnetted, 3 subnets
C 172.16.50.0 is directly connected, Serial0.2
O 172.16.20.0 [110/128] via 172.16.70.1, 00:07:24, Serial0.1
C 172.16.70.0 is directly connected, Serial0.1
O*E2 0.0.0.0/0 [110/1] via 172.16.50.1, 00:07:24, Serial0.2
r1#
Although while I was setting this up, I had a couple of ideas as to why
(synchronization) they
went away as I went through the lab and compared Halabi's config with mine.
In short, I think your right on the money with your configs.
Maybe someone like Howard Berkowitz can step in and shed some light.
Tim
-----Original Message-----
From: Banlan Chen [mailto:banlan.chen@lycos.com]
Sent: Friday, January 10, 2003 2:29 PM
To: ccielab@groupstudy.com
Subject: BGP question from Halabi's book
Hi Group,
Did anybody do the labs from the book? Around page 402, there is a topic
about "BGP Policies Conflicting with the Internet Default". Under this
topic, Default route has been injected into different IGP. In order to avoid
the loop, he uesd several methods.
My question is at page 408, the RTA's routing table has a default route from
BGP, but from my lab (I use same senario), I got default route from OSPF
peer(RTG). Since RTA got default route from IBGP whose AD is 200, whereas
OSPF's AD is 110, I think RTA's route table should have the default route
from OSPF. What do you think?
Any idea will be great appriciate.
Banlan
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