Want to Connect Two OSPF Area 0--Urgent

Unanswered Question
May 6th, 2008

Hi Friend

I have query , How to connect two backbone area 0 in ospf, my design like this.

R1( &

Both company is running via ospf 0 and now both company want to merge and make it single, how can i do ?



I have this problem too.
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JORGE RODRIGUEZ Tue, 05/06/2008 - 20:49

There is much more to it in trying to connect two companies under different OSPF domains backbone routers, you also have to take under consideration how each company is spread out geographically under their own OSPF, much more thorough information remains to be gather from each company to get a better picture and come up with a merger strategy. Have you consider connecting the two using bgp instead and redistribute ospf into bgp.

You could merge the two backbone area 0s routers but it could be a nightmare if each company is using multiple ospf areas or even having overlapping networks,I would look into bgp which would be the easiest way to merging the two companies.





minumathur Wed, 05/07/2008 - 12:45

Hi Friend

Can i implement one routing protocol like ( RIP V2 ) between two backbone area 0 and redistribute ospf routes into ripv2 and get it done, Please suggest ... other alternative if anyone have.. this is very urgent...



Giuseppe Larosa Thu, 05/08/2008 - 02:13


first of all you need to examine the two OSPF databases and to find out what IP subnets are overlapping.

If you can set up two direct links between two routers of company A and two routers of company B. You can use a network from 172.16.x.y for these links (RFC 1918)

Configure a second ospf process (use a different router-id and a different ospf process number) on the two routers of company A and have in area 0 for process ospf 2 a network statement for 172.16.x.y.

Add a network statement for 172.16.x.y area 0 on the two border routers of company B.

IP subnets not overlapping can be redistributed from ospf process 1 to ospf process 2 with two route-maps A-to-B and B-to-A.

For overlapping subnets you need to NAT them on both sides you could use address pools taken from 172.24.x.y (RFC 1918) for subnets of Company A to make them reachable from Company B. and 172.25.x.y for subnets of company B as seen on company A.

You can configure configure NAT on the four routers. You need to advertise the NAT address pools inside the two OSPF processes.

hope to help



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