Telstra - SIP Connect (SIP Trunk)

System Preparation

Before starting to configure your Telstra SIP Connect SIP Trunk in 3CX, you must first make sure that your network is set up correctly.

What you will need to have before reading this section is the following:

• The Telstra Edge Router IP.
• The Primary and Secondary Telstra DNS Servers.
• The SBC FQDN Telstra has instructed you to connect to.

All of the above will be provided to you by your Telstra representative.

Network Topology

In order to use a Telstra SIP Trunk, you will be provided with a Edge Router device that will be managed by Telstra and through which you will be exchanging VoIP traffic with the Telstra network. The network topology should look similar to the following:

In the above network topology example, the 3CX Server will be accessing the internet via the Internet GW, while all SIP Trunk related traffic will be traversing the Telstra Edge Router device.

3CX Server NIC Setup

Following the above example, the NIC on the 3CX Server will have the Internet GW as its Default Gateway. In order however for the SIP Trunk traffic to traverse the Telstra Edge Router, there is some configuration that is required.

The first thing you must do is add the 2 Telstra DNS Servers as primary and secondary in the NIC settings of the 3CX Server. The DNS IPs will be provided to you by your Telstra representative.

The reason this is necessary is because Telstra provides you with a specific Outbound Proxy which is only resolvable by these DNS Servers.

Important! Failing to set the DNS servers will result in your SIP Trunk not registering.

Adding Static Routes

Next you must add some static routes so that the traffic from the 3CX server towards the Telstra servers is routed out through the correct Gateway. To do this on a Windows OS, you would open a command prompt using the “Run as Administrator” option, then run the following commands:

• Static Routes for the DNS Servers:
  route -p add [Primary DNS IP] mask 255.255.255.255 METRIC 1 [Telstra Edge Router IP]
  route -p add [Secondary DNS IP] mask 255.255.255.255 METRIC 1 [Telstra Edge Router IP]
  
  e.g.:
  route -p add 10.86.113.20 mask 255.255.255.255 METRIC 1 10.2.2.1
  route -p add 10.86.114.20 mask 255.255.255.255 METRIC 1 10.2.2.1
  
  After adding these static routes, it is recommended that you check that the 2 DNS servers are reachable from the 3CX Server and that they accessed through the correct Gateway. To do this you can use the “tracert” command from the command prompt.
  
• Static Route for Telstra SBC:
  Next you must find the IP of the Outbound Proxy (SBC) that Telstra has instructed you to connect to. To do this open the command prompt and type in the command:
          nslookup [SBC FQDN] [Primary Telstra DNS Server]
  e.g.:
          nslookup sbc-cw.ipvs.net 10.86.113.20
  

Once you have the IP address, you need to add a static route for this IP as well to be routed through the Telstra Edge Router IP:
route -p add [Telstra SBC IP] mask 255.255.255.255 METRIC 1 [Telstra Edge Router IP]

e.g.:
route -p add 192.168.175.132 mask 255.255.255.255 METRIC 1 10.2.2.1

After adding this static route, it is again recommended that you check if the SBC IP is reachable from the 3CX Server and that is accessed through the correct Gateway using the “tracert” command.

Important Notes:

• The IPs and FQDNs in this section used as examples may vary from the ones you must use. If you are unsure which information you must use, contact your Telstra representative.
• The Internal LAN IP that your Telstra Edge Router will have must be according to RFC1918 (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16).

Configuring the Trunk with 3CX

The general instructions outlining how to add a new SIP Trunk to your 3CX installation can be found here.

Collecting 3CX Configuration Information

After the network configuration, it is time to set up your Telstra SIP Connect SIP Trunk in 3CX. Before starting, make sure you have the following information available as given to you by your Telstra representative in the RRAS Order:

• Outbound Proxy/SBC FQDN
• SIP Realm/Domain
• Trunk Pilot Number
• Authentication User ID
• Authentication User Password
• Number range/DIDs

With the above information you can proceed to the next section which explains how you use this information to configure the Trunk in 3CX.

Adding the Trunk

Go to “SIP Trunks” and select “Add SIP Trunk”

• Select Country: AU
• Select Provider in your Country: Telstra - SIP Connect (SIP Trunk)
• Main trunk number: Enter the Trunk Pilot Number in a 9-digit format (National excluding the leading ‘0’), e.g. 280743741
• Press OK

Under the “General” tab in the “Authentication” section, fill in the information as shown below.

Important! In the “Registrar” field, make sure that “transport-tcp.” is proceeding the SIP Realm as you enter it. If for example your SIP Realm is “sip.contoso.com”, you would enter “transport-tcp.sip.contoso.com”.

At this point you may also want to adjust the value of “Number of SIM Calls” to match the number of SIP Channels your Telstra account allows for.

Once you have filled in these fields as given to you by Telstra, scroll to the top of the page and press OK. At this point if you refresh the page you should see your Telstra Trunk appear as Registered.

Remarks

On the Telstra network, there is a Malicious Call Trace (MCT) function that can be initiated. The Feature Access Code for this function is *57. In order for this functions to work correctly for endpoints via 3CX, you must do the following:

• Make sure you have created an Outbound Rule in 3CX that allows for dialing this number.
• The default 3CX dial code for CLIR is *5 which conflicts with this function. You must go to the Management Console → Settings → Dial Codes and change the “Block Outbound Caller ID” dial code to a different value.

About Telstra

Telstra’s SIP Trunking solution is simple, flexible and gives users complete control over their service as they can manage it themselves from the online portal. With a wide range of plans and options to choose from Telstra’s SIP Trunking solution is ideal for any Australian business being a start-up or a large enterprise.

Last Updated

This document was last updated on 10 July 2023

https://www.3cx.com/docs/sip-trunk/telstra-sip-connect-australia/