Using DDNS in Chan_SIp external IP sending Local Lan ip

We are trying to figure out DDNS and how to implement it for failover for SIP trunks.

I tested with our provider ESI on two different systems.

Here is how I set it up, on both systems.
Enabled DDNS in System Admin Pro, got correct external IP
Went to Asterisk SIP settings Put into General and Chan_SIp settings the DDNS url in the External IP , left the Type of IP the same at static. Applied Config. Made test calls. On my system the calls went OUT fine, On the customers system the call was rejected by ESI. I did a TCPdump and found out that the failed call was sending the internal LAN IP of the phone system.

Here is the system info for both:

My system.
Sys Admin Pro

Customer system
Sys Admin Pro

When using a DDNS address, the type should be Dynamic (IIRC). Remember that Chan-SIP cannot change IP addresses without an Asterisk restart, so this needs to be configured as well.

You may also be seeing NAT setting problem with your phone configuration, since the internal address is leaking out onto the Internet. Make sure all of your system components are set up to use NAT, just to make sure the external address is used when appropriate.

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