Connect a Mitel MiVoice (3300 MXE / MiVoice Business) to a NumberGroup SIP trunk

This is the setup for adding a NumberGroup SIP trunk to Mitel MiVoice Business (the platform formerly known as Mitel 3300 MXE, also branded as MiVoice Office 250, MX-ONE, etc — all share the same SIP-peer plumbing). Tested against MCD 9.x / MiVB R10–R14. Plan an hour for the first one; the routing forms are pernickety but the values themselves are straightforward.

When you ask us to set up the trunk, mention you want the User-Agent Type to "RFC3261 Standard Trunk" and Send Numbers As to "International (+xx)". Mitel handles E.164 cleanly across SIP peer forms and the +44 presentation matches what your CESID / outbound URI patterns will assume.

Prerequisites

• MiVoice Business R10 or later (older releases work but the form names differ)
• SIP licences applied — confirm under System Administration Tool → Licences
• Network Element configured for the public-facing IP
• If you're behind NAT, a Session Border Controller (Mitel MBG / Ribbon SBC SWe Lite) is strongly recommended. Direct-public registration works but Mitel's NAT handling is fragile

Step 1: SIP Peer Profile

System Administration Tool → SIP → SIP Peer Profile → Add.

Basic tab

• SIP Peer Profile Label: NUMBERGROUP
• Network Element: your public-facing NE
• Address Type: FQDN
• Address: sip.numbergroup.com
• Port: 5060
• Transport: UDP
• Maximum Simultaneous Calls: match your trunk's Fraud Detection ceiling (we'll have agreed this with you)

Trunk Attributes tab

• Number of Trunks: same as Max Simultaneous Calls
• SIP Trunk Service Number: any unused number, e.g. 9100
• Class of Service: your standard outgoing CoS
• Class of Restriction: your standard outgoing COR
• SMDR Variant: None (unless you use SMDR)

Signaling and Header Manipulation tab

• Send 180 Ringing: Yes
• Inbound Call Identifier From Header: From: header
• Outgoing From URI: Use SIP User ID
• Caller ID (URI & FROM) Privacy: Off
• Reroute Outbound on Originating Trunk: Off

Voice and Fax tab

• Audio Codecs (in order): PCMU, PCMA, G.722
• DTMF Method: RFC2833
• Fax: T.38 if you actually use fax; otherwise G.711 pass-through

Security tab

• SRTP: Off (unless you've set Voice Mode = secure encrypted voice on the trunk)
• Registration Authentication: Required
• Username: T-AAAAAA-NNN (e.g. T-102377-001)
• Password: your trunk password from the email we send you
• Realm: sip.numbergroup.com

Step 2: Network Element / IP Trunk

SIP → Network Element → Add if not already there. Tie the SIP Peer to a Trunk Group.

• Trunk Group Name: NUMBERGROUP_OUT
• Outgoing: Yes
• Incoming: Yes
• Dialled Digits — Outgoing: leave default
• CESID (Calling Emergency Service ID): your main DDI in E.164 (+441****1262) — this is what the network sees as your address for 999

Step 3: ARS — outbound routing

Automatic Route Selection → Digit Modification:

• Strip the access digit (typically 9) and the leading 0
• Prepend +44 — Mitel handles the + cleanly

ARS → Routes:

• Route Number: 1 (first available)
• Route Type: SIP Trunk
• Trunk Group: NUMBERGROUP_OUT
• Digit Modification: the one you defined above
• COR Group: your standard outbound COR

ARS → Digits Dialled: add patterns for UK and international:

• 901[1-9] (UK area codes after 9-0 access prefix)
• 907 (UK mobiles after 9-0)
• 9011 or 900 (international after 9-00 access prefix)
• Emergency: route 999/112/101 unconditionally with CESID set

Step 4: inbound routing

Inbound DDIs land as E.164 (+441****1262). In the SIP Peer Profile's Inbound DID tab, map each full DDI to an internal extension or to your Auto Attendant pilot.

• +441214001262 → 2001 (main switchboard) → Auto Attendant 9000
• +441214001263 → 2002 (sales hunt group)
• +441214001264 → 2003 (direct dial to Jane)

If you'd rather route by last-4-digits, use the Significant Digits setting on the SIP Peer to strip the +441 prefix down to the four-digit user part.

Mitel-specific gotchas

Codec re-negotiation on hold

Mitel changes codec on hold/resume by default. With NumberGroup's trunk this usually works, but if you see one-way audio after a held call resumes, set Send SDP on Hold to No in the SIP Peer Profile's Signaling tab.

MiAUDA / Multi-vendor SIP Phone licences

Internal SIP phones registering to MiVB need an MiAUDA licence. Doesn't affect the trunk to NumberGroup but worth knowing — if your internal SIP phones aren't registering, this is usually the cause.

Port 5060 vs 5070

MiVB sometimes defaults internal SIP signalling to 5070 to avoid conflict with the public trunk on 5060. Confirm under System Options → SIP Signaling Port.

MBG / SBC required for public Internet trunks

Mitel's direct-Internet SIP support is officially unsupported for trunking. If you don't already have a Mitel Border Gateway, you should — the MBG acts as the SBC and handles NAT/security cleanly. For smaller sites, Ribbon SBC SWe Lite is a supported alternative.

Firewall

• UDP 5060 outbound to sip.numbergroup.com
• UDP 5060–5061 inbound on the SBC public IP
• UDP 32768–61000 for RTP (Mitel default range — varies by release)
• Disable SIP ALG on the WAN edge

Debugging

• System Administration Tool → SIP Reports → SIP Trace — live SIP message capture with filtering
• SIP Reports → Peer Status — registration state, last error, in-progress calls
• Ring us — we'll see the registration state and recent INVITE results our side and can tell you what's being rejected

Set fraud caps

Mitel is a high-value target for dial-through fraud — keep the Fraud Detection thresholds tight (50% above real peak), block international by default in ARS, and re-enable specific countries only as needed. See our telecom fraud guide.

Source: the device navigation in this guide follows Mitel Document Center — MiVoice Business. We keep the click-path with the manufacturer so it stays current — the NumberGroup trunk values above are the part specific to your account.