Router R1 sits inside OSPF area 1. Router R2 redistributes an E1 route into OSPF for prefix
2.2.2.0/24, with external metric 20. Router R22 redistributes an E2 route for the same
prefix/length, external metric 10. Under what conditions will R1 choose as its best route the
route through R22?
A.
R1 will always choose the route through R22.
B.
As long as R1’s best internal OSPF cost to reach R22 is less than 10.
C.
As long as R1’s best internal OSPF cost to reach R22 is less than 20.
D.
R1 will never choose the route through R22 if the E1 route through R2 is available.
Explanation:
Routers add internal and external costs for E1 routes and use only external costs for E2
routes, so the cost for the route through R22 will always be lower. However, for a given
prefix/length, OSPF always prefers intra-area routes first, then interarea, then E1, and finally,
E2, all regardless of metriC.