We are using Wireless Broadband and having ISDN as a back up for Internet.
AS I said for Internet so we can not create any tunnel with service provider.
My router is connected with wireless CPE through ethernet which never goes down unless and until we have some break the connection between 2 manualy or some pysical faliure which is rare actually. And we can not use dynamic routing protocol with our ISP.
I would appreciate if some body can provide suggest be how can I have ISDN as a auto fallback for Wrieless connection?
Such scenarios are discussed several times in this post.
For this you can use the feature called reliable static routes using object tracking.
Using this you can configure the router to send periodic pings to the other end ip of the service provider. As long as this ping works fine, the defautl route that you have configured in the router will be taking effect. Once the router sees that no long the ping to the specified host is working, the default route in your router will be removed and the next best route available in your routing table ( floating static route pointing to the ISDN) will take effect.