Migration from EIGRP to OSPF

This example points out the steps required to be carried out for migrating from EIGRP routing protocol to OSPF routing protocol.

Sample EIGRP network:





All routers are configured for EIGRP with the similar configuration given below:
EIGRP Configuration

router eigrp 1
network 0.0.0.0
no auto-summary
passive-interface fastethernet 0/1 ! Clients connected to this interface
!

OSPF deployment:


Now, through proper planning, the flat EIGRP network is converted to multi-area OSPF network as below-

Here, OSPF is enabled on a per-interface basis. Also, the administrative-distance of OSPF is made higher   to 200 or above. The reason being the administrative-distance of EIGRP internal routes is 90, but the AD of EIGRP external routes is 170.

The following is the sample configuration on router R4-

OSPF configuration on R4

Since the AD of OSPF is changed to high values, at this stage, OSPF will not replace EIGRP. However, OSPF speakers will start to form neighbor relationships.


The following outputs are taken from router R4 which shows the neighbors it has formed relationship with. Also, notice that there are no OSPF routes in the routing table.

Once EIGRP configuration is removed from all routers, OSPF routes are installed in the routing table with high AD.

The complete migration is seamless and no outage is noticed by the clients. http://www.nil.com/ipcorner/ChangingRoutingProtocol/