I'm having a problem with configuring OSPF on a couple of routers.
I have a packet tracer activity i am working on: one customer router connected to a remote router via a serial link and also connected to the ISP router via another serial link.
How do i disable OSPF updates to the ISP router but allow the OSPF updates to the remote router.
Below is a link to the packet tracer file i am working on.
user mode password : cisco
privilledge exec password : class
vty password : cisco
I checked the file. OSPF updates are already disabled between the CENTRAL router and the ISP. The CENTRAL router did not establish an adjacency with the ISP router, it only did it with the BRANCH router. You can check that by typing:
[code:1]CENTRAL# show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
192.168.128.97 1 FULL/- 00:00:38 10.1.1.1 Serial0/0/0[/code:1]
As you can see above the only adjacent router is the BRANCH (192.168.128.97).
However, the ISP router is configured with 2 static routes that point to the inside network:
[code:1]ip route 10.1.1.0 255.255.255.252 Serial0/0/1
ip route 192.168.1.0 255.255.255.0 Serial0/0/1[/code:1]
Thats why when you list routes on the ISP, you get:
[code:1]ISP#show 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, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
10.0.0.0/30 is subnetted, 1 subnets
S 10.1.1.0 is directly connected, Serial0/0/1
S 192.168.1.0/24 is directly connected, Serial0/0/1
188.8.131.52/30 is subnetted, 1 subnets
C 184.108.40.206 is directly connected, Serial0/0/1
220.127.116.11/30 is subnetted, 1 subnets
C 18.104.22.168 is directly connected, FastEthernet0/0[/code:1]
Notice here the S flag which indicate that the routes came from a static route. If it came from OSPF, it should have been flaged by O.
What about if a router has a serial link and a fastethernet link, how then do i disable OSPF updates from being advertised to the fastethernet link. I want to do this for the purpose of minimizing bandwidth usage.
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Re: OSPF configuration problem
9 years 5 months ago #30784
It doesn't matter what or how many interfaces the router has, as long as it's config does NOT include ospf statements (with the same AREA number 0), the router will NOT participate in OSPF for that area.
In your example, the ISP router did not have any OSPF statements in it's config. Thats why it did not participate in OSPF.