Which statement about the split-horizon rule for distance vector routing protocols is true?
A. A router advertises a route to an unreachable network with an infinite metric.
B. A router does not advertise routes to any neighboring router.
C. A router advertises routes back out the interface on which it learned them with an infinite metric.
D. A router does not advertise routes back out the interface on which it learned them.
D
https://geek-university.com/ccna/split-horizon-explained/
Split horizon is one of the methods used by distance vector routing protocols to avoid routing loops. The principle is simple – a router will not advertise a route back onto the interface from which it was learned. Split horizon is enabled on interfaces by default.