From: George Zhang (GeorgeZhang@xxxxxxxxxxxxxxxxxx)
Date: Fri Jan 26 2001 - 12:20:13 GMT-3
First of all, thank every one who has responded my post.
I spent a few more hours investigating the problem. I found four solutions to
the problem. There are some gotchas need to be aware of in similar kind of sce
narios. Following is a brief summary of my findings.
1. Solution #1: As suggested by Llie, configuring distribute-list on Tokyo and
London under EIGRP to block 182.18.0.0 coming in to the serial interfaces conn
ected to NewYork. Thank s, Llie.
2. Solution #2: Configuring distribute-list on NewYork under EIGRP to block 18
2.18.0.0 going out of the serial interfaces connected to NewYork.
3. Solution #3: Configuring distribute-list on NewYork under EIGRP to block 18
2.18.0.0 coming out of ospf 100. This was actually what I did if you check my
previous post. Why it did not work for me? See explanation below.
4. Solution #4: Turn EIGRP auto-summary on NewYonk. This is my favorite soluti
on because the configuration is the simplest. See explanation below. This is
contrary to some people suggested.
Explanation:
Why O 182.18.0.0 is redistributed to Tokyo and London?
When summarization is configured on NewYork under OSPF, an OSPF summary route (
O 182.18.0.0/16) pointing to Null 0 is added to the route table. This route is
redistributed by NewYok to Tokyo and London because redistribution of OSPF is
configured under EIGRP. That's why solution#1, #2, and #3 work. There is one
gotcha here. If you configure the distribute-list last, the route (O 182.18.0.
0/16) is already distributed to Tokyo and London. It won't go away right way.
Will it go away eventually? I don't know. The way to get rid of that route i
s to shut/no shut the serial interfaces between Tokyo, London and NewYork or re
boot the routers. That's exactly why solution#3 did not work for me.
Why solution#4 works?
When auto-summary is turned on, an EIGRP summary route (E 182.18.0.0/16) pointi
ng to Null0 will be added to the route table. Because EIGRP has lower administ
ration distance, the OSPF summary route (O 182.18.0.0/16) will be kicked out of
the routing table. Because O 182.18.0.0 is not in the route table of NewYork
, so it will not be redistributed to Tokyo and London. No distributed-list nee
ds to be configured. The gotcha for this approach is that, if you turn off aut
o-summary of EIGRP first, configure summarization under OSPF second, then an su
mmary route (O 182.18.0.0/16) will be added to the route table of NewYork. The
n, you turn on EIGRP auto-summary. The summary route (O 182.18.0.0/16) will st
ay in the route table. It does not go away by itself. It's still get redistri
buted to Tokyo and London. I had to reboot NewYork to get rid of that stubborn
summary route. I don't know if "no router ospf 100" and reconfigure it will g
et rid of that summary route. Could someone test it?
George
>>> "George Zhang" <GeorgeZhang@alliant-energy.com> 01/24/01 01:12PM >>>
I am reading through the "Advanced IP routing in Cisco Networks" by Terry Slat
tery. I have also been doing the labs in the book along the way. I just did o
ne of the two 6-router labs in Chapter 7 of the book - example 10 EIGRP and OSP
F redistribution. I used the Mentorlab 3645 to do this lab. Everything works
as expected with only one exception. When I checked the routing table on Tokyo
and London, I saw the following route is in the routing table:
In tokyo's route table:
D EX 182.18.0.0/16 [170/2195456] via 182.18.1.2, 00:09:04, Serial0
In London's route table:
D EX 182.18.0.0/16 [170/2195456] via 182.18.2.1, 00:07:35, Serial1
I tried to use distribute-list on router NewYork to filter it out. But it did
not work. I guess that the first question is, should it be there? If it shoul
d be there, why? If it should not be there, how to get rid of it? It really
bothers me.
Could someone please explain it?
The configurations and route tables of the three mentioned routers are attached
for your info.
Thanks.
George
NewYork#s
Building configuration...
Current configuration:
!
version 11.3
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname NewYork
!
enable password cisco
!
ip subnet-zero
ip tcp synwait-time 5
no ip domain-lookup
!
interface Loopback0
ip address 172.16.253.5 255.255.255.252
!
interface Ethernet0
ip address 172.16.254.2 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial0
ip address 182.18.2.1 255.255.255.0
ip summary-address eigrp 200 172.16.0.0 255.255.0.0
no ip route-cache
no ip mroute-cache
!
interface Serial1
ip address 182.18.1.2 255.255.255.0
ip summary-address eigrp 200 172.16.0.0 255.255.0.0
no ip route-cache
no ip mroute-cache
clockrate 1300000
!
router eigrp 200
redistribute ospf 1 metric 100000 100 255 1 1500
network 182.18.0.0
distribute-list 2 out ospf 1
no auto-summary
!
router ospf 1
summary-address 182.18.0.0 255.255.0.0
redistribute eigrp 200 metric 100 subnets
network 172.16.254.2 0.0.0.0 area 0
distribute-list 1 out eigrp 200
!
ip classless
!
access-list 1 deny 172.16.0.0
access-list 1 permit any
access-list 2 permit 172.16.0.0
!
line con 0
exec-timeout 0 0
privilege level 15
password cisco
logging synchronous
line aux 0
password cisco
login
transport input all
line vty 0 4
password cisco
login
!
end
NewYork#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, * - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks
C 172.16.254.0/24 is directly connected, Ethernet0
C 172.16.253.4/30 is directly connected, Loopback0
O IA 172.16.1.0/24 [110/74] via 172.16.254.1, 00:04:09, Ethernet0
O IA 172.16.2.0/24 [110/138] via 172.16.254.1, 00:05:24, Ethernet0
182.18.0.0/16 is variably subnetted, 6 subnets, 2 masks
D 182.18.4.0/24 [90/2195456] via 182.18.1.1, 00:08:28, Serial1
D 182.18.5.0/24 [90/2195456] via 182.18.2.2, 00:08:28, Serial0
O 182.18.0.0/16 is a summary, 00:08:25, Null0
C 182.18.1.0/24 is directly connected, Serial1
C 182.18.2.0/24 is directly connected, Serial0
D 182.18.3.0/24 [90/2681856] via 182.18.1.1, 00:08:29, Serial1
[90/2681856] via 182.18.2.2, 00:08:29, Serial0
Tokyo#s
Building configuration...
Current configuration:
!
version 11.3
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname Tokyo
!
enable password cisco
!
ip subnet-zero
ip tcp synwait-time 5
no ip domain-lookup
!
!
!
!
interface Ethernet0
ip address 182.18.4.1 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial0
ip address 182.18.1.1 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial1
ip address 182.18.3.2 255.255.255.0
no ip route-cache
no ip mroute-cache
clockrate 1300000
!
router eigrp 200
network 182.18.0.0
!
ip classless
!
!
line con 0
exec-timeout 0 0
privilege level 15
password cisco
logging synchronous
line aux 0
password cisco
login
transport input all
line vty 0 4
password cisco
login
!
end
Tokyo#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, * - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
182.18.0.0/16 is variably subnetted, 6 subnets, 2 masks
C 182.18.4.0/24 is directly connected, Ethernet0
D 182.18.5.0/24 [90/2195456] via 182.18.3.1, 00:09:04, Serial1
D EX 182.18.0.0/16 [170/2195456] via 182.18.1.2, 00:09:04, Serial0
C 182.18.1.0/24 is directly connected, Serial0
D 182.18.2.0/24 [90/2681856] via 182.18.3.1, 00:09:06, Serial1
[90/2681856] via 182.18.1.2, 00:09:06, Serial0
C 182.18.3.0/24 is directly connected, Serial1
London#s
Building configuration...
Current configuration:
!
version 11.3
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname London
!
enable password cisco
!
ip subnet-zero
ip tcp synwait-time 5
no ip domain-lookup
!
!
!
!
interface Ethernet0
ip address 182.18.5.1 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial0
ip address 182.18.3.1 255.255.255.0
no ip route-cache
no ip mroute-cache
!
interface Serial1
ip address 182.18.2.2 255.255.255.0
no ip route-cache
no ip mroute-cache
clockrate 1300000
!
router eigrp 200
network 182.18.0.0
!
ip classless
!
!
line con 0
exec-timeout 0 0
privilege level 15
password cisco
logging synchronous
line aux 0
password cisco
login
transport input all
line vty 0 4
password cisco
login
!
end
London#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, * - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
182.18.0.0/16 is variably subnetted, 6 subnets, 2 masks
D 182.18.4.0/24 [90/2195456] via 182.18.3.2, 00:09:36, Serial0
C 182.18.5.0/24 is directly connected, Ethernet0
D EX 182.18.0.0/16 [170/2195456] via 182.18.2.1, 00:07:35, Serial1
D 182.18.1.0/24 [90/2681856] via 182.18.3.2, 00:09:36, Serial0
[90/2681856] via 182.18.2.1, 00:09:36, Serial1
C 182.18.2.0/24 is directly connected, Serial1
C 182.18.3.0/24 is directly connected, Serial0
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