Question

R2 sits between an OSPF domain (area 0) and an EIGRP AS 100 domain and performs two-way redistribution. R4, also connected to both domains, redistributes as well. Users report that a subnet 10.10.50.0/24 originating in EIGRP is being learned in OSPF, then redistributed back into EIGRP through R4, causing a suboptimal path and intermittent reachability. Which action on R4 BEST prevents the original EIGRP route from being reinjected back into EIGRP as an external route?

Accepted Answer

Tag routes as they are redistributed from EIGRP into OSPF, and on redistribution from OSPF into EIGRP deny any route carrying that tag with a route map

Answer

Increase the administrative distance of external EIGRP routes to 255 on R4 so the routes are never installed

Answer

Enable split horizon on all EIGRP interfaces on both R2 and R4 to stop the route from being advertised back

Answer

Configure a summary route for 10.10.50.0/24 on R4 pointing to null0 to suppress the reinjection