[asterisk-users] asterisk slows down when unplugging internet cable with VoIP lines

[Giorgio Incantalupo]

Hi,
I have an Asterisk 1.2.9.1 on a Debian Sarge distro connected to a VoIP 
provider via internet.
I noticed Asterisk gets slow and  behaves in strange manner if I unplug 
my internet cable from the PBX: for example I get incoming calls after 
seconds or I get no audio during calls.
I thought it was something connected to DNS resolution so I put VoIP 
provider addresses inside /etc/hosts but still have slow problems.
I made some tests adding registrations to providers inside sip.conf 
keeping my PBX disconnected from internet: after a "sip reload" the CLI 
simply stay freezed waiting for something. Trying to "sip reload" gives 
a message Asterisk is still waiting to perform the last reload. A real mess!
I read on internet, inside dns.h file reference, Asterisk is using 
synchronous dns functions...infact a note explains that:
"Asterisk DNS is synchronus at this time. This means that if your DNS 
does not work properly, Asterisk might not start properly or a channel 
may lock"
How can it be? If this should be true this would be a big problem with 
VoIP lines since losing internet connections is not so uncommon (if so, 
why nobody else got this trouble?)
Is it possible to bypass this behaviour or should I avoid VoIP lines??

TIA

Giorgio Incantalupo