Problem
VoipNow 3, which by default has DNS caching enabled, comes with a different version of Kamailio.
The problem is that, in some situations, customers manually set an IP and a Hostname in /etc/hosts.
This hostname may be used either when configuring a SIP trunk or to specify the location of a PBX behind an extension.
If this was done, then VoipNow 3 won't parse /etc/hosts and that channel will remain unregistered.
Requirements for 4PSA VoipNow 3 installation
In VoipNow 3 /etc/kamailio/kamailio.cfg contains a setting called: use_dns_cache, which by default is set to "yes". This means that all DNS request results will be cached.
Also note that if enabled, /etc/hosts will be completely bypassed and all requests will be go directly to the system configured (/etc/resolv.conf) dns server. This implies that the Nameservers set in /etc/resolv.conf should be able to resolve properly the channel hostname.
By setting use_dns_cache to "no" the server running kamailio will do the name resolving (and use /etc/hosts also).
It is recommended in production servers to have: use_dns_cache=yes
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