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Having problems with DDR. Anyone doing VPN with a branch using an ISDN connection to the internet? I would specifically like to know if anyone has discovered a way of forcing the ISDN to dial automatically/repeatedly until a connection is acheived. Cheers!

Community Member

Re: VPN and DDR (ISDN)

I am currently Doing the exact same thing..... but waiting for hardware. Using a 1720.....waiting for the WIC-1B-U card. I have been reading from cisco's site (search DDR vpn ISDN)and have found some good info about setting up the DDR....

(dial on demand routing)

Check out

It explains the dial backup for leased lines...but doesnt get into the VPN turf..

If you have any input you can email me directly at

or respond....Thanks

PS when i figure it out I will post actions and results.

Community Member

Re: VPN and DDR (ISDN)

I've been working on this since posting and I've discovered that the native ISDN config does not automatically dial (it needs what Cisco calls "intereting traffic" to initiate the attempt). The only way to ensure automatic dial attempts would be to configure RIP or OSPF to periodically send out updates or 'hello' packets (which incidentally are considered interesting traffic). Since this would add overhead to the router CPU and any machine that is targeted to receive these packets, it just isn't feasible.

Thanks for the link! This is another topic I have started looking into! Let me know what you find. Cheers!

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