Conversion EIGRP->OSPF in production environment

[news2010a]

Imagine I have a production network running EIGRP, total of 5 routers. (2 routers in the data center, 1 router each branch office). I would like to setup the main office as "Area 0" and the respective branch offices I would setup as "Area subnet#_branch_office". I am wondering whether setting up Stub areas in the branch offices could be a good approach.

What would be the best way to approach a migration to OSPF ? Do you start with redistribution from EIGRP to OSPF, or would you just re-advertise networks running EIGRP with OSPF ? I would appreciate directions on this.

[sundar.palaniappan · Accepted solution]

Marlon,

Migrating from EIGRP to OSPF should be an easy process. You can configure OSPF concurrently while EIGRP is running and that wouldn't impact routing as EIGRP routes are preferred over OSPF because it has a lower (better) admin distance than OSPF. Once you are done fully configuring OSPF then you can start removing EIGRP. At this point, the EIGRP route will be lost and OSPF route should replace it in the routing table. The only exception to this is if you have external EIGRP route then the OSPF route might take its place and can create problems. But, there are ways even this problem can be addressed.

As far as your question about stub routing is concerned, it's not a bad idea to configure as a stub if the network is a hub-and-spoke. Infact, you can go level further and configure them as totally-stub routers and that way the branches will only learn a default route from the hub device.

HTH

Sundar