ISDN Dialup to 2 x Seperate Routers

Oct 06, 2006 2 Replies
D

I have 2 x 2800 Routers, each has a ISDN (BRI) network card installed (WIC-1BS/T).



Each BRI has a separate phone number.



On a remote site I have and ADSL router (Cisco 877) and ISDN backup (801) router.



I want to build a config for my ISDN remote site router to allow me to dial the 2800A and if I get an engaged tone dial 2800B. Both 2800A and 2800B sit on the same LAN.



I have seen a number of examples that provide me with legacy dialer map configurations pointing to the same endpoint, e.g.



dialer map ip 172.20.10.1 name AAAAAA broadcast 5551111 dialer map ip 172.20.10.1 name AAAAAA broadcast 5551112



In this case the endpoint 172.20.10.1 sits on 1 x router and this router has



2 x ISDN phone numbers. As my phone numbers are split over separate routers, can I just add a second dialer map statement pointing at the 2nd router. If so how would I then route to my end destination.

I intended to run RIP v2 and block the 'uninteresting traffic' with a dailer list.



Regards



Darren


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A

You can use multiple dialer maps to connect to different routers, but I would strongly recommend using dialer profiles instead.

Aaron

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V

This can be done reliably using dialer profiles, dialer watch, and filtering of "trigger" routes to force dialer watch to pick the right dialer to use. You do need to test carefully, however, as there are some really obscure bugs in dialer watch that only show up when using multiple levels of backup, but you should be OK with two levels. I have one client set up to dial one ISDN link immediately, a second ISDN link if the first does not connect within 5 seconds, and use a modem to place a POTS call if neither ISDN connects within 30 seconds.

Two problems which we have seen are:

Dialers will randomly hang and cease to be functional. Rebooting the router brings everything back into operation. One more reason for routine testing of backup links.

Dialer watch will not redial a dropped call if the watched route was never in the routing table to begin with. This required adding a bit of dial on demand to the dialer watch configuration to force a DDR dial. This error is very platform specific (e.g., S/T ISDN WIC works, U ISDN WIC fails!).

You'll have to determine for yourself whether or not your hardware has the necessary features and horsepower to do the job.

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