Cannot dial out via ISDN if the ADSL is down, any solution?

I’ve 1 PRI ISDN used via chan_modem, 3 register lines into sip.conf, 6 voip phone.

If i start asterisk and the ADSL is down the 6 voip phones are unable to call each other and also to place call via ISDN because they are not registered.

Is there any solution to this problem?

Does your DNS work when the dsl line is down? Maybe you should use ip addresses instead of domain names. Running a caching name server could help.

No it does not works, i’ll give a try putting fixed ip address into /etc/hosts
is this all the problem? i dunno … it seems that asterisk will not go onto the other phone registration until the first “register =>” are completed.