Redunant WAN link with Cisco 1720

[admin_2]

We have a Cisco 1720 with two WIC:

1 x ISDN

1 x ADSL

How do we configure the router to achieve the following:

The ADSL link should be the primary Internet connection. If the ADSL link fails traffic should be sent through the ISDN line (permanent).

The problem seems to be that the line protocol on the ADSL link can be up, although no traffic gets through to the internet (eg. problems in the ADSL Service Providers network).

How can we get the router to automatically switch to the ISDN line in this scenario?

We are able to use the Router at the end of the ISDN line if necessary. (eg configure the router at the end of the ISDN line to probe the ADSL connection from outside). Not sure if this is necessary.

[#2]

The only option available to you are

to trigger dialing based on the loss

of routing updates from the ADSL link.

Since the line protocol doesn't go down,

it's data failure (ie routing updates)

that would have to trigger dialing.

See dialer watch under the documentation.