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

B、The RIPv2 dynamic routing protocol cannot be used across a Frame Relay network.

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

D、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.

E、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.