Sip Registration Intermittent

Hello

Build - FREEPBX 2.8.0.1, with Asterisk (Ver. 1.6.2.7)

Im finding my sip registration is very intermitant with my VOIPFONE Trunk

If I save the VOIPFONE Trunk this resolves the problem, but only for a short while, after this save, using the sip show registry command i can see that the registration is happening after 45 seconds

pbx*CLI> sip show registry

Host dnsmgr Username Refresh State Reg.Time
sip.voipfone.co.uk:5060 Y 3016093 45 Registered Mon, 02 Aug 2010 07:07:31
1 SIP registrations.
pbx*CLI> sip show registry

Host dnsmgr Username Refresh State Reg.Time
sip.voipfone.co.uk:5060 Y 3016093 45 Registered Mon, 02 Aug 2010 07:08:16
1 SIP registrations.
pbx*CLI>

While this is happening incoming calls work fine, however after short while registration fails (ie the Reg Time doesn not change) and when this occurs incoming calls cease, however sip show registry still shows registered…as below

pbx*CLI> sip show registry

Host dnsmgr Username Refresh State Reg.Time
sip.voipfone.co.uk:5060 Y 30136093 45 Registered Mon, 02 Aug 2010 07:12:03
1 SIP registrations.

The problem sometimes resolves it’s self if i wait long enough !, however I need the registration to be reliable

It looks like registration is not being updated reliably…

Has anyone experiance similar problems ???

Any suggestions would be appreciated

Following on from this i have now disabled dnsmgr…

Asterisk keeps doing dnsmgr_lookup for sip.voipfone.co.uk approx every 45 seconds…while this is happening everything is fine, output below

pbx*CLI> sip show registry
Host dnsmgr Username Refresh State Reg.Time
sip.voipfone.co.uk:5060 N 30136093 45 Registered Mon, 02 Aug 2010 12:22:03
1 SIP registrations.

However after a short while doing dnsmgr_lookup stops and can only be restarted by sip reload…

Does anyone have any ideass why would dnsmgr_lookup stop ??

Thank you