I failed this question due to
point-to-point subinterface should've been configured on R5 to track the link status
Can some one explian this please... why point to point ..?
It's related with task 2.6 (really hidden trap :P )
Vadim gave good explanation:
Task 2.1: Whenever you configure the backup interface command you need to ask yourself what will cause the line protocol of the interface to go down. For Frame Relay the line protocol of the main interface is based on receiving LMI keepalive from the Frame Relay cloud. For Frame Relay subinterfaces it is based on the circuit status.You enabled FR EEKs only on R5's DLCI503:Rack19R5#show run int s0/0interface Serial0/0 no ip address encapsulation frame-relay no fair-queue frame-relay traffic-shaping frame-relay interface-dlci 503 ppp Virtual-Template1 class DLC503However, it's not the only DLCI assigned to R5's S0/0 interface by the FR switch via LMI. The following DLCIs are also assigned to R5's S0/0 interface - 501, 502, 504 and 513. You can use the show frame-relay pvc | include DLCI command to find out all DLCIs assigned to the interface.R5's FR link will not go down until all these PVCs are in the INACTIVE, DELETED or EEK DOWN state.If the Frame Relay circuit between R3 and R5 goes down, the other 4 DLCIs will still be in the ACTIVE state. Thus, the FR link will be up and R5's S0/1 interface will remain in the STANDBY state.