A. Allows interfaces to share common IP addresses.
B. Allows an interface to remain up without the aid of keepalives.
C. Allows a router to send routing and not receive updates via that interface.
D. Allows a routing protocol to forward updates that is missing its IP address.
E. Allows a router to receive routing updates on an interface but not send updates via that interface.

A. Spanning Tree Protocol
B. Shortest path first tree
C. Link-state advertisements (LSA)
D. Hold-down timers
E. Split horizon
F. VRRP