External IP Address?

Notice the difference in the IP addresses displayed under SYS ADMIN / DDNS and under SIP SETTINGS. Under CHAN SIP, I have DDNS set with my own DDNS address entered. What does my PBX think is the current external IP address? How is it updated?

They’re two separate things.

The DDNS update is for your DDNS, and the SIP Settings are for SIP. If you go into the chan_pjsip or chan_sip settings you have a finer-grained control over how you want to configure your SIP stack.

The answer to the ‘how does it get this address’ is http://myip.freepbx.org:5060/whatismyip.php

24.n.n.246 is a windows box (Windows Small Business Server 2003) ( be careful here with publishing IP addresses, the Chinese are watching :wink: ), how/why is that involved ?

Dicko, depends on which port you access. I guess you tried 443.

Still no answer to the point that the IP displayed under SIP Settings is not up to date with my external IP. If the PBX updates its external address dynamically, what is the SIP setting good for as it is obviously not keeping up.

You update that manually. DDNS does not update the SIP Settings page for you and it does not say it does anywhere.

Not to be a pain about this but trying to be helpful… what is the SIP Settings IP entries use in a DDNS environment, except to be confusing. Where is the operative IP address for the box displayed?

I assume the Sys Admin / DDNS display is simply the current DDNS “service” address. In SIP Settings / Chan SIP the DDNS name is entered and it is assumed this keeps the box IP up to date but how often and how can its operation be monitored / verified.

If the SIP service address is being updated behind the scenes, why not update it in SIP Settings to avoid confusion. Otherwise one can look at that address and think there is a problem updating the box IP address.

Where is all this explained? Am I wrong to think there are some unobvious aspects?

The idea is to use NAT if, as you are, behind a firewall,.You need to use the externhost=foo.dyndns.net syntax with an appropriate “refresh rate” (dynamic IP in FreePBX talk) if you rely on a DDNS service instead of the externip=n.n.n.n, it’s all in the wiki., did you read it yet?

I’m sorry if I wasn’t clear earlier, but they are TOTALLY UNRELATED. This is why you’re confused. I’m actually somewhat puzzled as to what makes you think they ARE related.

One is for DDNS. The other is for Sip. As I said in my first post, if you want finer grained control over that, please look at the SIP Driver page itself.

It is. Look at the Sip Channel page.

I am offering a Gold Star to the first person to get my point. (hint, you can get a clue by looking at my original post).

go to ssh to your server, and do

route -n

(if you’re not root, use sudo in front of the command or login as root)

see where any of your IP shown there, appear.

I have got your point, and you STILL HAVE NOT LOOKED AT THE SIP DRIVER PAGE. Which is where this is actually configured.

There are little questionmarks that you can hover over, that answers your questions. If you are unsure of the phrasing, then please ask for clarification.

Again, I have no idea what you’re on about. One is for setting DDNS, one is for setting SIP. They both happen to be IP addresses, but so is the IP address of your phone, your desktop, and your tablet. They are different things, as are these.

Note: the above is a 13 screenshot

Thank you for your reply Rob,

  1. Where is the “SIP Driver” page? Do you mean Asterisk SIP Settings /Chan SIP?

  2. Do you notice my point that the SIP IP is not my current external IP. I understand the basic concepts, I just am pointing out that they are not in sync and it may be confusing. I am also pointing out that the “actual” box IP address being used by SIP is also not displayed or obvious. Clearly it is not the one showing on the SIP Settings page or it would not be working.

So… it may be useful to make that sync or come up with some other way to monitor whit the box is using for an IP when in DDNS mode. Also, visibility to the DDNS refresh process could be comforting, like how often does it update. To my knowledge, the VOIP trunk calls need the correct external IP to set up the call. So visibility into how it is maintained in DDNS mode is useful.
As I said, the out of sync addresses brought up all this discussion.

That IP address doesn’t update. That’s an override address. If you want it to automatically update, you’ll need to enable that per driver.


If you are using the Sysadmin supplied DDNS, that is what you see in your first screenshot. You’re not using that, so we can’t really help you there.

That’s configurable on the DDNS page.

Normally, FreePBX just looks after it itself, if you use the Sysadmin supplied DDNS. As you’re not, there’s not really much we can tell you.

Is the answer that the box only accesses the DDNS IP real time, when it needs an external address it just looks it up using the DDNS address and doesn’t need the address to be “set”? So, there is really no “actual external PBX address” except as needed.

So I know this thread is old.

The guys question is:

Do you have to even set an ip under External Address if you are using the proper Chan SIP settings using yes, dynamic ip?

The guy even says that he is using DDNS.

I know this place is crap posted with generic configuration issues but this seems like a pretty easy question to answer.

Considering this was one of the first results in Google when looking up if this matters…it might make a difference to answer this question.

If someone puts a DDNS setting in…

What still uses the ip under External Address on the first NAT config page?

The problem with the questions and answers is that people interchangeably use the term “DDNS Hostname” and “DDNS IP Address”.

If someone wants to use DDNS, they put the DDNS Hostname in the External Address box. Do not put in the current external IP address. The system checks every 15 minutes to see if the DDNS Address has changed and the system makes the appropriate adjustments.

The second problem is that (historically) the external address is supplied by the browser and not the actual server, so if you connect from outside the network (like I do from my management console at my office) and supply the IP address that gets reported, it will be wrong. The address supplied is the external address on my office network and not the address of the server. Important note - this behavior may have changed or may change at any moment. The point is to make sure the external address you are using for NAT is the correct address. If it changes or you don’t know the address, don’t guess - you have to get this right.

IMHO - there is no excuse for setting up a PBX (especially with inbound traffic) on a system that doesn’t get a dedicated IP address. I understand there are teenagers here that don’t have the resources to do this right, but there’s been a lot of effort expended on this system for things that I personally shouldn’t be as high a priority as it’s been.

The excuse is cost so if the DDNS support strategy works that is enough ( How you choose to operate is interesting, your judgement about others behavior is not).

Dyndns business cost $160/month most service providers charge ~$20/month what is the attraction to dropping an extra $140 every month

There is information around the internet for setting up Amazon route53 as a ddns service for $1-2/mo if you are looking to save a few bucks

I remain a little puzzled by the existence of two settings for DDNS. Can we have only one?

Also, once, the FreePBX DDNS server was down and the PBX was not reachable. I requested that a alternate DDNS address be available as a fallback even though the Freepbx one has been very reliable. Better safe that sorry.