CompTIA Network+ (N10-009)Network ImplementationMedium
A router learns a route to 192.168.50.0/24 via both OSPF and EIGRP with different metrics. Assuming default administrative distances, which route will the router install in its routing table?
- AThe EIGRP route, because EIGRP has an AD of 90
- BThe OSPF route, because OSPF has an AD of 110
- CBoth routes are installed simultaneously as a load-balanced path
- DThe OSPF route, because OSPF has an AD of 90
Show answer & explanationAnswer & explanation
Correct answer: A. The EIGRP route, because EIGRP has an AD of 90
EIGRP's default administrative distance for internal routes is 90, while OSPF's default AD is 110. Since a lower AD indicates a more trusted source, the router installs the EIGRP route over OSPF when both advertise the same destination network.
Why the other options are wrong
- B. OSPF's AD is correctly stated as 110, but it is not the preferred route.
- C. Routers do not load balance between different routing protocols with different ADs by default.
- D. OSPF's AD is 110, not 90, so this reasoning is incorrect.
Administrative Distance
A value representing the trustworthiness of a routing information source; lower AD values are preferred when multiple protocols advertise the same destination.
- Connected routes: AD 0; static routes: AD 1
- EIGRP internal: AD 90; OSPF: AD 110; RIP: AD 120
- Router selects lowest AD route among competing sources
Memory trick: Lower AD = more trusted, like a lower golf score wins.