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Telephony signalling and routing

Article ID: 768
Last updated: 10 Aug, 2021

This section describes how to configure Digital Fax to properly interact with the PBX or voice gateway in  terms of protocols and routing.

Voip configuration can be controlled through the "IP Routes" page. From the home page select "Fax" => "Application Settings" => "IP Routes".

WARNING: you have to stop and restart the Digital Fax service from the web interface after any change done in this page.

Telephony Protocol and Negotiation

Here you can choose between SIP and H.323. Adjust your PBX configuration accordingly.

The two options on negotiation ("Allow G.711 for outgoing faxes" and "Disable T.38 for incoming faxes") are to be left unchecked for most telephony systems. Please check the PBX configuration section for additional information.

Outgoing routing

Default Route

By default, Digital Fax routes all outgoing faxes to one IP address. This is called the Default Route, and should be the IP address of the PBX or Voice Gateway enabled to send the faxes.

Warning: If the Default Route is not properly configured, Digital Fax will not work.

Digital Fax T.38 engine can route the outgoing fax calls to many different IP address. Each of these addresses is a physical device which can be a PBX or a Voice Gateway supporting T.38 or G.711 passthorugh fax transmission.

Multiple routes and Least Cost Routing

Digital Fax can manage multiple routes, i.e. multiple Voice Gateways or PBX, based on the first digits of the CALLED number. E.g. you can configure it so that all the outgoing fax calls that have a recipient's telephone number beginning by 06 are routed to a specific gateway. The faxes that do not match this rule will be routed to the Default Route.

In the "Set IP Routes" dialog, just enter the prefix and the IP and click "Add".

Fallback Routes for high availability

You can add the same route multiple times associated with different IP addresses. Digital Fax will try to route outgoing faxes towards the first destination. If the routing fails, it will try the next one. When no more IP addresses associated to the same prefix are found, the call is sent to the default route.

Adding a prefixes to outgoing faxes

Digital Fax can add a prefix to outgoing fax numbers (for LCR or any other aim) through the Ip Routes Page. In the Routing Parameters box select the "Global" PBX routing type, enter the prefix and press "Save". This parameter will affect only off-net outgoing faxes, see below.

This option will affect Print To Fax, Web To Fax and Email To Fax.

Network Routing Type

Set this option on "External only". If you want to send faxes form Digital Fax to internal ATAs, please refer to the advanced configuration chapter.

Article ID: 768
Last updated: 10 Aug, 2021
Revision: 3
Views: 919
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