Refer to the exhibit. S0/0 on R1 is configured as a multipoint interface to communicate with R2
and R3 in this hub-and-spoke Frame Relay topology. While testing this configuration, a technician
notes that pings are successful from hosts on the 172.16.1.0/24 network to hosts on both the
172.16.2.0/25 and 172.16.2.128/25 networks. However, pings between hosts on the 172.16.2.0/25
and 172.16.2.128/25 networks are not successful. What could explain this connectivity problem?

A.
Split horizon is preventing R2 from learning about the R3 networks and R3 from learning about
the R2 networks.

B.
The 172.16.3.0/29 network used on the Frame Relay links is creating a discontiguous network
between the R2 and R3 router subnetworks.

C.
The RIP v2 dynamic routing protocol cannot be used across a Frame Relay network.

D.
The ip subnet-zero command has been issued on the R1 router.

E.
The 172.16.2.0/25 and 172.16.2.128/25 networks are overlapping networks that can be seen by
R1, but not between R2 and R3.

Explanation:
The problem in this situation is related to split horizon , which reduces incorrect routing information
and routing overhead in a distance-vector network by enforcing the rule that information cannot be
sent back in the direction from which it was received. In other words, the routing protocol
differentiates which interface a network route was learned on, and once it determines this, it won’t
advertise the route back out of that same interface.
in a spoke and hub Frame Relay topology, the Frame Relay interface for the hub router must have
split-horizon processing disabled. Otherwise, the spoke routers never receive each other’s routes.