I have configured a 1720 router, IOS 12.2(2), for leased line and isdn as backup. The leased line is fiber optic which terminates at the fast ethernet through a converter. Similarly the optic fiber is connected at the layer 3 switch at the ISP side. Now i have configured the router in such a way that if the leased line goes down; i.e, fast ethernet goes down, isdn should come up automatically. But the isdn is not coming up automatically. There is no problem with the isdn line or configuration. When the router is rebooted after pulling the fastethernet cable from the router, the isdn will come up. If any one have faced this type of problem and have solved it, please help me.
How do you have the backup configured? Are you doing "backup interface isdnX"? If so I don't think it will work because your fastethernet interface probably never goes down. You may want to get a TAC case opened up and attached to feature request CSCds88143. Either that or inquire about it with your local account team. Is there any way you can get some kind of route feed from your ISP? Is so you could use dialer watch. You may want to check out this page on cco about backup ddr:
in the fast ethernet interface I have configured "backup interface bri0". I am considering opening a TAC case, but before that giving a try here. FastEthernet is generally stable, but this backup is used if anything happens in worst case. I used to pull the cable from the fast ethernet interface and i have noticed that the interface is going down. So its not an issue of fastethernet not going down. I have also checked up the route in the isp side and found no problem there. I will check with dialer watch today and let you know.
I believe dialer watch is a good solution. The other thing to remember is that ethernet will send keepalives by default. Try using the no keepalives on your ethernet port and then pull it. The router will not send keepalives out the interface and should appear down.
If you use "no keep" under an ethernet interface it will come up/up even if it isn't plugged into anything. So that will not work. Dialer watch will only work if you can get a route feed from the isp. or possible one through a tunnel to another router you have connected to the internet.
Did you get an answer to this issue. I am currently seeing a similar problemwith a 1700 runnig 12.2.(5). In my case once the router decides the ISDN Layer 1 and Layer 2 are inactive the router will not reactivate. Debug dialer display the message "No dialer available".
I've seen this before when using a 10Mbps LAN link over fibre with ISDN backup using 2600's. The problem is that the Fibre Optic Transceiver interface keeps the router interface up/up despite pulling the fibre.
I ended up using OSPF with passive interface BRI0/0 and a floating static route with an Admin distance higher than that of OSPF (default 110)
This may require a router at the ISP end but mine was point to point fibre i.e between buildings and not to an ISP. Hope this is of some help.
If you want to mail me I can send you the configs from both ends?
The problem is that I won't be able to run any routing protocol between the router and ISP router.