07-15-2010 12:39 AM - edited 03-04-2019 09:04 AM
Hi networkers,
This is a scenario I'm sure some of you guys have encountered.
I have two routers. Each one has a link to the telco provider. One is 10M (line1) and the other is 2M (line2). R1 is connected to line1, and R2 is connected to line2. They are backbone area routers.
The issue is the following: most of the LANs of our branches are learned through R2. But some routes are learned through R1.
I first thought it's a matter of OSPF costs. Both my routers are connected to the telco, so I thought that R2, when it computes routes to branches, finds that it's preferable to reach them through ISP PE2 (connected on line2) than through R1 (which has a better WAN bandwidth).
Telco told me to configure "filters" as they said :-), I thought of distribute lists and route-maps.
07-15-2010 12:59 AM
Hi wass.aouadi,
You can start checking the OSPF DB via "sh ip ospf database" on both R1 and R2. Especially R1, check whether it receives both from R2 and from ISP and compare it.
rgds, dsu
07-15-2010 02:19 AM
07-15-2010 02:34 AM
What about
sh ip ospf database summary 10.101.0.0
sh ip ospf database summary 10.101.0.32
sh ip ospf database external 10.101.0.0
sh ip ospf database external 10.101.0.32
on both R1 and R2
07-15-2010 03:26 AM
07-15-2010 03:55 AM
Issue: R1 will prefer 10.101.0.32 from 192.168.100.9 over 192.168.100.1 due to its intra-area path.
To Do:
1. You can make 192.168.100.9 not to advertise 10.101.0.32, or
2. you can filter LSA3 on R1 and R2 from appearing.
07-15-2010 11:59 PM
I did some shut/no shut on R1 and R2 interfaces. Here's what I noticed:
So I noticed that OSPF process prefers inter-area LSAs over External LSA.
the questions here are:
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