Specifications

3CXTunnel/3CXSessionBorderController
Introduction
3CX includes the 3CX Tunnel to allow for easier bridging of remote 3CX Phone Systems and
connectingremoteextensions.The3CXTunnelcombinesallSIP(signaling)andRTP(media)VoIP
Packetsfromonelocationanddeliversthemtoandfromanotherlocation(typicallythePBXServer)
using a custom TCP protocol. This simple concept allows 3CX to overcome firewall or telecom
providerissues.The3CXTunnelcanbeusedforthefollowingreasons:
● ResolveissuesofNATTraversalatboththeremoteandthePBXlocation.
● SimplifiedFirewallconfigurationatboththeremoteandthePBXlocation.
● OvercomedifficultieswithISPsthatblockVoIPTrafficbasedonportnumbers.
● AllowsVoIPoverWiFiinsomerestrictedlocations,suchasHotelrooms.
● “Fixes” Firewalls thatcannot handle VoIP traffic correctlyor which are very problematic to
configurecorrectly,suchas:
○ MicrosoftISAServer
Note: Presence information does not get carriedthrough the Tunnel to the remote network as of
yet.MakesurethattheHTTP/HTTPSportsyouhavechosenduringtheinstallationareopenonthe
PBXserverside.
HowitWorks
The3CXTunnel
The image above demonstrates how the 3CX Tunnel works. In this example, the 3CX Phone
SystemisonIPAddress10.0.0.181,andlistensonTCPport5090(bydefault)forincomingTunnel
traffic.WemustsetupasinglePortForwardingruleontheModemorNAT/FirewallDevice,tellingit
that all incoming TCP traffic received on port 5090 should be delivered to LAN IP Address
10.0.0.181.
Theremotesetupisshownonthelefthandsideofthecloud.Inthisexample,themachinewithIP
addressof192.168.0.2has3CXPhoneinstalled.WewillneedtotelltheVoIPPhonethepublicIP
addressofthePBXServer(whichinthiscaseis213.165.190.51),andalsotheprivateIPaddress
ofthePBXServer(whichinthiscaseis10.0.0.181).Sincethe3CXPhonewillbydefaultusethe
standard port numbers used by 3CX Phone System, typically no further configuration will be
necessary!
ConfiguringtheTunnel
Wewillusetheaboveexamplein“Howthe3CXTunnelWorks”toconfigureatunnelconnection.
Step1–ConfigurethePBX
Inthe3CXManagementConsole,gotothe“Settings”>“Network”>“3CXTunnel”tab.
1. ConfiguretheTunnelPassword(e.g.“r6W4Qi”)
2. Set the Local IP to the Local IP Address of the NIC, which will be receiving tunnel