Core Issue
When routes are redistributed into the Enhanced Interior Gateway Routing Protocol (EIGRP), external routes are tagged with the Originating router field. This field is the router ID of the router redistributing the routes.
The router ID is selected from the highest IP address assigned to a loopback interface. If no loopback addresses are configured, the router ID is selected from the highest IP address assigned to any other interface. When multiple routers use the same router ID, the routes are not installed in the routing table, resulting in routing failures.
Resolution
To prevent duplicate router IDs, ensure that the IP address on the interface being used as the router ID is unique between the EIGRP routers.
To manually configure a router ID for EIGRP, issue the eigrp router-id command from the router configuration mode of EIGRP.
For more information, refer to Preventing Duplicate EIGRP Router IDs.
