The SipXproxy sipXproxy is able to add the an Alert-Info Header to SIP INVITE Messages to tell phones to play a different ring tone for internal and external calls. By default it default this feature is enabled and your Proxy should look like this.:
This mechanic proxy plugin looks inside at the FROM-Header and checks if the from domain is equal to the SIP Domain of SipX. Calls the sipXcom system. If calls are not from the SIP domain, calls from a Gateway or Session Border Controller could be are thus detected as external calls.
Some phones use the information of the FROM-Header to fill their call history (e.g. Yealink T4x-Series). In this special case the phones (on re-dial from the phone) may try to call directly via the gateway and fail due to security settings.
To get this working it is necessary to set the SIP Domain inside the FROM-Header, which would otherwise break to the Alert-Info detection.
An alternative Way way to mark this calls as external is to set a parameter to an extra parameter in the SBC or Gateway in the FROM-Header which is called "x-sipx-alert-info=external".
You can adds this add this tag or the Alert-Info Header directly in your gateway. For example on , in a Patton Gateway you can't add a customer header, but header but you can modify the FROM.:
If you your devices are configured this way, the INVITE Message that your Phone will receive will look more or less like this the following and the phone plays will play a different ring tones tone for external and vs. internal calls.