Section 4: ISDN (6 Points)
Configure ISDN on R3 and R5 using PPP. R3 and R5 should be able to ping each other across the ISDN link.
If you configured this correctly as shown in Example 4-31, you have scored 3 points.
Make sure that only when the ISDN link is up that it will pass routing protocol across the link.
The ISDN link should pass routing protocol only when R5-s0/1 and/or R5-fa0/0 and/or R5-fa0/1 is down. Consider that the routing protocol can pass through the ISDN link when topology changes happen.
The key to configuring as requested is to avoid the ISDN to advertise or pass traffic through the link when the other physical interfaces on ...