DDNS Issues

I am running Freebx 16.0.26, with asterisk version 19.6.0. I am trying to use a dynamic IP enabled, but whenever my isp changes my address the system will not allow calls unless i go and change the external address in general sip settings. I have my router registered to my DDNS but the system never adjusts. Channel Sip settings have NAT yes, dynamic IP, 120 sec refresh.

What configuration mistake am I doing so that the system will router to the DDNS and not the external address? Any help would be appreciated.

Hi Duncanidaho,

I might be able to help. I have a PBX on a Dynamic IP and it is working fine.

I have an FQDN in the external address under sip general and in channel sip.

I use duckdns for my external IP lookup and I am not depending on my router to do it. Is your router updating quickly when your IP changes?

Are you using chan_sip or pjsip?

Are you using the DDNS section is system admin? I don’t bother with that.

What are your DNS servers?

Anything in /etc/hosts?

what about in /etc/asterisk/sip_nat.conf ?


I tried to see if I could get a static IP from my ISP and they said they do not offer that. They suggested using a VPN for a static IP.

I am not that familiar with the technical side so i may have to request assistance from Freepbx.


Thats for the note. Yes I do use ddns from sysadmin. I am not highly technical so I may need to hire someone to assist. My isp does not offer static IP and suggested vpn. I am using my router ddns option and it does register.


You don’t need a static IP to get this to work.

Where are you getting your VoIP trunks from?

Can you post screenshots? (block out your IP address)

Post a screenshot of the General SIP settings and the SIP Legacy Settings. Chan_SIP.

I use two, one uses SIp and one uses pjsip.
Perhaps you can tell me how to set the General SIP Legacy and Channel Sip and I can attempt to have a similar setup. Ill have to find all the info you are looking for. Thanks

Here is my DDNS from sysadmin

Should I put my ddns address in the force IP?

Okay, so turn off the DDNS service.

Now from your router for the DDNS to work, you should be generating a public accessible FQDN?

myip.mydomain.com for example.

On the general sip settings, does it detect your proper public IP? If I get the correct public IP, I then put my FQDN in this field and save. Don’t click detect again.

Then on the sip legacy tab, I set it to this:

Anytime I reboot the system within 2 to 3 minutes, it knows my new IP address.

I have made the changes. The system still works, however, my external ISP has not changed. So I will monitor the external to see if it functions with a change of external IP. Thanks

Reboot the router. that’s the best way to test

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