FreePBX 15 behind NAT: HowTo setup dynamic external IP config?

[HELSup (Hs)]

Hi all!

My FreePBX 15 is up and running behind a Fritz!Box via NAT.
Everything worked fine for some time but now I found that my external “static” IP is not really static and it may be changed.
So I can’t no longer use in SIP Settings → General SIP Settings → NAT Settings a fixed “External Address” via “Detect Network settings”.

I want to use our own web server to get my external IP address and no external service.
For example

wget http://some.web.address/cgi-bin/addr.cgi -q -O - | awk ‘/REMOTE_ADDR/ {print$2}’

I looked at the documentation and the Forums but I found no information how to use such a setup.

Any clue?

TIA,
HS

[cynjut (Dave Burgess)]

It sounds like you need to do two things:

1. Change to PJ-SIP - if Chan-SIP looses it’s IP address, it goes catatonic and you have to reboot Asterisk to get it back.
2. Add a Dynamic DNS entry to allow the graceful transition of the external address when it changes.

[HELSup (Hs)]

1. I use actually chan_pjsip

2. Is it not possible to use a custom shell command as shown in my initial mail? How about changing a configuration via shell command after an IP change occurred? This would be pretty easy to set up but I have no clue what configuration has to be changed.

[cynjut (Dave Burgess)]

@HELSup

Is it not possible to use a custom shell command as shown in my initial mail? How about changing a configuration via shell command after an IP change occurred?

Yes, that is possible and has been discussed here are length. @comtech and @pitzkey (IIRC) both have provided considerable Intellectual Property on this subject in the past.

[HELSup (Hs)]

Thanks for your help. I will dig more into the forum to find related posts next week.

[HELSup (Hs)]

My solution is now the usage of a DNS name in the External Address field of the SIP settings.
This name is resolved via “/etc/hosts” entry.
Now I use a cron job to check frequently the external IP. In case it did change the hosts file is updated.

[bitbanger]

You don’t need the cron job (and shell script, I assume) to modify /etc/hosts. While chan_sip “always” supported a FQDN in FPBX External Address, chan_pjsip just got this capability relatively recently (some time in 2018).

See this blog post:

https://blogs.asterisk.org/2018/01/10/pjsip-dns-manager-dnsmgr-full-dynamic-hostname-support-coming-soon/

and this Community thread:

PJSIP update external IP address automatically?

How do I have my external IP address in Freepbx updated automatically when using PJSIP? I am behind a dual wan situation and have DDNS, where my FQDN updates automatically. I understand that there is the External Address setting under General SIP Settings, where you can press the Detect Network Settings to update the external IP address manually. If you want that to happen automatically for chansip you can provide a Dynamic Host under Chansip Settings and set a refresh intervall. How do I do…

I set up FPBX 14 with a FQDN in External Address in 11/2018 – works fine.

(This assumes that you have dynamic DNS for the FQDN. Many routers can provide dynamic DNS updates.)