All SIP phones unregister when internet goes down

I experience all SIP phones to unregister from asterisk, when internet goes down. I have a couple of SIP trunks defined in sip.conf. I found somewhere on the forum, that trunk registrations should be defined using IP addresses, not names like I do.
It is a live system, and internet connection is stable for most of the time, but when it dies, phones on local network can not talk to each other, which is nonsense.

Can anybody give me any hints on this issue??? Can DNS resolution cause a whole SIP service (even local phones) to go down???
thanks in advance


I may be wrong, but I think the problem is that asterisk gets ‘stuck’ trying to resolve the DNS names, and that stops the system from being usable. I have experienced the same problem. There is more about it here