If your Frame Relay network fails, allow R4 to dial into R1. Use passwords that are difficult to detect. Ensure R4 dials out after 5 seconds of Frame Relay failure. If the Frame Relay network restores, keep the call connected for a further 45 seconds before disconnecting. OSPF is required over the ISDN network when a call is established. Do not configure any Layer 3 addressing on the physical ISDN interfaces.
