Note 1: The 3CX fax server is designed to handle faxing via only one entity. Due to this you cannot have faxing capabilities from both PSTN Gateways and VOIP Providers at the same time.

Note 2: For a FOIP overview see http://wiki.3cx.com/documentation/voip-telecom/fax-over-ip.

Note 3: For a list of supported VOIP providers for FOIP please see <link>

Note 4: This functionality requires 3CX PhoneSystem V8.0 build 10116 or later.

Requirements

·         To set up FOIP (Fax over IP) with a VoIP Provider, a static external (public) IP address is needed.

·         In addition to the other ports necessary for VoIP communications for SIP and RTP, port 10000 TCP and UDP needs to be forwarded from your Firewall / Router to the 3CX Server IP.

·         Running 3CX PhoneSystem WITHOUT STUN is strongly recommended in this configuration, since it eliminates STUN resolution as a possible point of failure. For configuration details to configure 3CX PhoneSystem to function WITHOUT STUN:

http://wiki.3cx.com/documentation/networking/when-and-how-to-disable-stun-on-3cx-phonesystem

Modifying the Fax server Configuration

3CX PhoneSystem is delivered with default settings for Fax functionality with PSTN Gateways. To achieve Fax functionality with VoIP Providers it will be necessary to customize the configuration files. For this example, we will assume that the 3CX PhoneSystem machine has private IP Address 10.0.0.181, public IP Address 213.214.215.216, and that the Fax Server is listening on the default port number 10000, which will need to be port-forwarded one-on-one across the WAN-to-LAN device.

Configuring the 3CX Fax Server global templates

 

1.     From 3CX Management Console, go to "Settings -> Provisioning Templates"

2.     Select Template Type "3CX Fax Server".

3.     Select Template Name "faxglb.cfg" and click edit

4.     In the [SIP] section:

a.     comment the "NAT support = FALSE" line by adding a ";" at the beginning of the line

b.     remove the ";" in front of "NAT support = TRUE" to enable NAT support

c.     remove the ";" in front of "(NAT) local SIP IP port = 5100" to enable this setting

5.     Click on the "Apply" button.

6.     A dialog box will appear asking you to save this file. Keep the file name the same and click the "OK" button. You will be asked to override this file. Click YES.

7.     From 3CX Management Console, go to "Settings -> Provisioning Templates" (again)

8.     Select Template Type "3CX Fax Server"

9.     Select Template Name "in_session.cfg" and click edit

10.   Many providers will give reject fax calls with "488 Media Unavailable" if both UDP and TCP are specified as options for T.38 Fax communications. To help improve interoperability we can restrict T.38 to UDP only. To achieve this, in the [General] section:

a.     comment the "kind of T.38 transport = UDP_TCP" line by inserting a ";" in front

b.     remove the ";" in front of "kind of T.38 transport = UDP" to enable this setting

11.   We now need to configure NAT traversal functionality for the Fax Server. To do this, we need to first enable the feature, and then specify the correct values in the NAT traversal parameters. In the [T.38 media address] section:

a.     To enable the NAT traversal feature:

                                          i.    remove the ";" in front of the "local media ip address" line

                                         ii.    remove the ";" in front of the "local media ip port = 10000" line

                                        iii.    remove the ";" in front of the "(nat) local media ip address" line

                                        iv.    remove the ";" in front of the "(nat) local media ip port = 10000" line

b.     To specify the correct NAT traversal parameters:

                                          i.    enter the local IP Address of the 3CX PhoneSystem machine in the "local media ip address" line (for this example: "local media ip address = 10.0.0.181")

 

Note: This value must be the same as the local IP Address assigned to the 3CX FAX Receiving service. You can view (and adjust) the "Fax Server Host" setting from the 3CX Management Console by going to "Settings->Fax"

 

                                         ii.    enter the public IP Address of the 3CX PhoneSystem machine in the "(nat) local media ip address" line (for this example: "(nat) local media ip address = 213.214.215.216")

 

Note: If you have configured your 3CX PhoneSystem to run with STUN disabled, this value must be the same as the public IP Address assigned to the 3CX PhoneSystem machine. You can view (and adjust) this in the "Public IP to specify in Contact and SDP" setting from the 3CX Management Console by going to "Settings->Network" and clicking on the "STUN Server" tab.

 

                                        iii.    the "local media port = 10000" line and the "(nat) local media ip port = 10000" should remain unchanged.

c.     Click on the "Apply" button.

d.     A dialog box will appear asking you to save this file. Keep the file name the same and click the "OK" button. You will be asked to override this file. Click YES.

Updating the 3CX Configuration for VOIP Provider faxing

Using the 3CX Management Console:

1.     Go to the "Settings->Advanced" page

2.     Click on the "Custom Parameters" tab

3.     Ensure that the option "FAXDIRECTSDP" is set to the value of 1, creating a new entry if necessary.

4.     Click on Apply to save changes.

Restart 3CX PhoneSystem

For the changes made above to kick in, you will need to restart all 3CX Services. You can achieve this from the 3CX Management Console from the "Services Status" page by clicking on the "Restart All" button.

Adjusting Inbound Routing to receive Faxes

Edit the VoIP provider ports or DID/DDI you want to receive faxes through and make sure that the Office/Out of Office destinations are set to forward to "Send fax to email of extension" and in the adjacent field, select either "888 Default FAX Extension" or some other Extension Number.

 

Note: Failure to use the "Send fax to email of extension" destination type will override the setting "FAXDIRECTSDP" and incoming faxes will fail.