ISDN switch information:
ISDN switch type: basic-5ess.
- R1: 0298017705
- R4: 0296307050
SPIDs are not required.
Configure the ISDN interfaces on R1 and R4 as follows:
When R1's S0 goes down, R1 should place an outgoing call to R4.
R4 cannot call R1 under any circumstance.
Use PPP encapsulation and the strongest authentication available.
Never bring up more than one B channel to ensure that costs are kept to a minimum.
When the Frame Relay link is restored, bring down the ISDN link after 25 minutes.
When the ISDN is active, all routers must be able to ping and telnet the local ISDN interfaces on R1 and R4.