A network already learns the path to 10.20.0.0/16 through OSPF. An administrator wants to add an IPv4 static route to the same prefix that stays out of the routing table while OSPF is healthy and only takes over if the OSPF route is withdrawn. Which administrative distance must be applied to that static route for it to behave as a floating static backup?
- AAn administrative distance of 1, because that is the default for a static route and guarantees it is preferred only when needed
- BAn administrative distance of 110, so it matches OSPF and shares the load with the dynamic route
- CAn administrative distance of 0, because that forces the route to be treated as directly connected and most trustworthy
- DAn administrative distance of 130, so it is less preferred than the OSPF route and only installs when OSPF is gone Correct
Why A is wrong: 1 is indeed the default static administrative distance, but it is lower than OSPF's 110, so this route would always win and replace the OSPF path rather than float behind it.
Why B is wrong: Matching OSPF's distance of 110 is tempting because it sounds like equal standing, but equal administrative distance from different sources is resolved unpredictably and does not produce a clean backup; a floating route must be strictly less preferred.
Why C is wrong: 0 is reserved for connected interfaces and cannot be assigned to a configured static route; even if it could, the most trusted distance would override OSPF entirely, which is the opposite of a backup.
Why D is correct: A floating static route must carry an administrative distance higher than the route it backs up; 130 exceeds OSPF's 110, so the static route is held in reserve and is installed only when the OSPF route disappears.