Sip Lines as a backup

[yesterdaysman]

I have a client that wants a back up line should his ISDN 30 go down (which has happened a few times) so I've recommended he gets some SIP lines as a backup.

is there anyway of setting as a default that if the ISDN goes down all calls will be routed to the SIP Lines?

 

[CarGoSki]

for outgoing you select the ars form that contains routing for the sip trunk. There is a field called Alternate Route

For incoming you have to have telco detect the down condition then route your numbers to the sip trunk.