We are pleased to announce a significant feature addition to the Protel LTS platform:  the ability to trunk multiple Protel PBX units together, allowing extension-to-extension dialing between any number of Protel systems, regardless of location.


To facilitate this, we have added a new type of trunk connection to the options available in the Protel administration menu, called PBX Peer.  When a PBX Peer trunk is configured on two Protel units, it enables users at one location to reach any user on the other PBX by entering a prefix dialing code + the remote extension number.  The PBX Peer trunk uses the IAX2 (Inter-Asterisk eXchange) protocol.  Unlike SIP, which uses a separate RTP port for the media (voice) stream, IAX uses a single port (4569) for both the signaling and voice stream payloads, which permits reliable point-to-point connections between PBX servers, even if they are each behind NAT routers and/or firewalls.   The IAX2 protocol has built-in multiplexing, allowing multiple concurrent calls to take place on a single trunk port without a significant increase in bandwidth overhead.


There is no limit to the number of PBX Peer trunks that can be created on a single Protel unit, making it possible to extension dial any number of remote locations by entering a unique prefix code before the extension number.  Since the prefix code identifies a unique PBX location, it does not matter if one site has extension numbers that duplicate numbers at other sites.


To deploy this, you will need to have administrative access to each of the Protel units that need to be trunked together, and each of these units needs to have a static public IP address.  If the PBX is behind a NAT router, you will need to have port 4569 UDP forwarded to the internal PBX LAN address in order for the IAX trunk connection to work.


The trunk creation interface screen looks like this:


NAME  This identifies the trunk in the local PBX.  It is also the username that the remote PBX uses when connecting to it. 

SECRET  Create a robust password here.  We recommend using a random string of at least 24 characters.  Use letters and numbers only, no punctuation or special characters.  This string will also need to be entered in the Password field of the trunk settings for the corresponding PBX Peer.

DIALING IDENTIFIER  This is the unique index digit (or digits) that instructs the PBX to use this trunk for a particular call.  To simplify dialing for users, we recommend using a single digit here, unless there are a large number of remote PBX Peers.  We have established the default feature access code as *8, though this can be modified in the Feature Code table.  To call an extension at another PBX that has a trunk index of 1, the user would dial *81xxxx.

DESTINATION ADDRESS  Enter the public IPv4 address of the PBX Peer.

USERNAME  The login name that the local PBX sends to the remote PBX, along with the password, to authenticate a connection to the peer.  This needs to exactly match the Trunk Name listed in the remote PBX.  It is case sensitive.

PASSWORD  This string should be copied from the “Secret” field of the remote PBX and pasted here.

MUSIC ON HOLD  You can assign any available MOH folder to be associated with this trunk, or you can leave this entry null.


DEPLOYMENT NOTES After the trunks have been created in both PBX units, you will need to execute a reload to activate them. 

If the Whitelist Firewall security system is active, you will need to disable and restart it so that the PBX Peer trunk IP address gets automatically added to the Whitelist.


ADDITIONAL FUNCTIONALITY   In addition to being able to directly connect to any extension on the Peer PBX, you can also dial other target destinations in the remote unit, including DIDs, call groups, ACD queues and conference bridges, using the same feature code prefix method.


Please let us know if you need any assistance with this new feature or if you have any questions.