CORETAN KELIK ENDRATNO

An administrator is configuring a router that will act as the hub in a frame Realy hub-and-spoke topology. What is the advantage of using point-to-point subinterfaces instead of a multipoint interface on this router?

A. It avoids split-horizon issues whith distance vector routing protocols.

B. Only one IP network address nedds to be used to communicate with all the spoke device.

C. Only a single physical interface is needed with point-to-point subinterfaces, whereas a multipoint interface logically combines multiple physical interface.

D. Point-to-point subinterfacec offer greater  security compared to a multipoint interface configuration.

Explaination :

Split horizon indicates that in distance vector routing protocol, once you learn of a route through an interface, advertise it as unreachable back through that same interface in order to avoid routing loops. In a NBMA network such as FR, for the hub-spoke topology, on the point-to-multipoint interface at the hub end, routing information from a PVC is virtually needed to advertise other PVCs, instead, the characteristics of split horizon will not allow for such advertise, which result in spill horizon issues. Only refer to IGRP, on the physical interface of FR, split horizon is disabled default. On the point-to-point sub-interface adn point-to-multipoint sub interface of FR, split horizon is enabled. So, split horizon usually happens to point-to multipoint sub-interface, there are several solutions to issue this problem : Using no ip split-horizon command to disable split horizon on point-to-multipoint sub-interface, but this method will cause routing loops that can be resolved by distribute-list through transforming point-to-multipoint sub-interface into point-to-point sub-interface, meanwhile, you should notice that each point-to-point sub-interface should use network address respectively.