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Connecting a 3CX (or other IP PBX) to ASH NET with a SIP trunk

If you run your own PBX such as 3CX, register it to ASH NET as a SIP trunk. All the numbers on your account are then delivered to the PBX through one registration, and you handle extensions and routing in the PBX.

1. Set the account to “Registered SIP Trunk”

Log in to the VoIP portal, open the Voice tab and choose Profiles in the left menu. Set the connection type to Registered SIP Trunk and choose your main number as the pilot number – the number the PBX registers with. Save the default profile. Every other number on the account now behaves as a DDI routed to the trunk, including numbers added later.

2. Add the trunk in 3CX

  1. In the 3CX admin console open SIP Trunks → Add SIP Trunk, select country Generic and Generic SIP Trunk, and enter the pilot number as the Main Trunk No.
  2. General tab: Registrar/Server/Gateway = sip2.ashnet.co.nz; Outbound Proxy = sip2.ashnet.co.nz; set the number of simultaneous calls for your plan.
  3. Authentication: Register/Account based; Authentication ID = the pilot number (digits only); Password = the SIP password for that number.
  4. Route inbound calls to the extension, ring group or IVR of your choice; add your other numbers on the DIDs tab and set caller ID rules on the Caller ID tab.
  5. Options tab: allow inbound and outbound calls, disable video if not needed, and untick Supports Re-Invite. Set the codec priority to G.722, then G.711 A-law, then G.729. To pass the original caller ID on diverted calls, set the P-Asserted-Identity user part to the original caller number.
  6. Click OK. After a few seconds the trunk should show a green (registered) icon.

3. Whitelist our addresses

3CX occasionally blacklists a trunk provider by mistake, taking the trunk offline. In Security → IP Blacklist add our SIP address range with the action Allow and an expiry far in the future – email [email protected] and we will send you the current range.

Codecs, DTMF and NAT

Use RFC 2833 for DTMF, keep SIP ALG off on the router in front of the PBX, and see NAT and SIP ALG if calls have no audio. For encrypted SIP (TLS) contact us for certificates and port details. Set-up of the PBX itself and its extensions is outside what our support team can cover – contact 3CX or your PBX reseller for that.

Still need help? Email [email protected] or log a ticket in the customer portal.