Grandstream UCM SIP Trunk Configuration

Overview

This guide walks you through configuring a Simtex SIP trunk on a Grandstream UCM series IP-PBX using a Register SIP Trunk with TCP transport. This guide covers both the UCM6200 series (UCM6202, UCM6204, UCM6208) and the newer UCM6300 series (UCM6301, UCM6302, UCM6304, UCM6308).

Grandstream UCM PBX systems are feature-rich, competitively priced IP-PBX appliances with a comprehensive web GUI — grandstream.com

What you'll need

• Your Simtex account number (e.g. 214XXXXXXX)
• Your Simtex SIP password
• Your allocated DIDs (phone numbers)
• Grandstream UCM with web GUI access

Step 1 — Create the SIP Trunk

1. Log into your UCM web GUI
2. Navigate to Extension/Trunk → VoIP Trunks
3. Click Create New SIP Trunk (or + Add SIP Trunk)
4. Set Type to Register SIP Trunk

Step 2 — Basic Settings

Configure the connection details on the Basic Settings tab:

Type:                Register SIP Trunk
Provider Name:       Simtex-SIP
Host Name:           siptcp.simtex.com.au
Username:            214XXXXXXX
Password:            XXXXXXXX
Auth ID:             214XXXXXXX
Caller ID:           61894883344  (your main DID)
Caller ID Name:      (your business name)
Keep Trunk CID:      Checked
NAT:                 Checked  (if UCM is behind a router)
Need Registration:   Checked
Maximum Channels:    (your purchased channel count)

Step 3 — Advanced Settings

After saving the Basic Settings, click the edit icon on your trunk, then click the Advanced Settings tab:

Transport and Proxy

Transport:           TCP
From Domain:         siptcp.simtex.com.au
From User:           214XXXXXXX

Codec Preference

Set the codec preference list. Select and reorder:

Priority 1:  PCMA  (G.711 A-Law / alaw)
Priority 2:  PCMU  (G.711 U-Law / ulaw)

Remove any unnecessary codecs from the enabled list.

DTMF and Signalling

DTMF Mode:                  RFC2833
Enable Heartbeat Detection: Checked
Heartbeat Frequency:        60 seconds
Send PAI Header:            Checked

Click Save, then Apply Changes at the top of the page. The trunk should register within a few seconds.

Step 4 — Outbound Routes

Outbound routes (calling rules) tell your UCM which numbers are allowed to be dialled externally and which trunk to use.

1. Navigate to Extension/Trunk → Outbound Routes
2. Click + Add
3. Enter a Calling Rule Name (e.g. “Simtex National”)
4. Under Use Trunk, select your Simtex-SIP trunk
5. Set the Pattern for the numbers this rule handles (see table below)
6. Set Privilege Level appropriately (ensure extensions have matching or higher privilege)
7. Click Save, then Apply Changes

Step 5 — Inbound Routes

Inbound routes direct incoming calls on your DIDs to the correct destination.

1. Navigate to Extension/Trunk → Inbound Routes
2. Click + Add
3. Under Trunks, select your Simtex-SIP trunk
4. Under Pattern (DID Pattern), enter the DID number in E.164 format without + (e.g. 61894883344) — or leave blank for a catch-all route
5. Set the Default Destination to the target extension, ring group, IVR, queue, or other destination
6. Click Save, then Apply Changes

Create a catch-all route first

Leave the Pattern field blank to create a catch-all route. This handles any inbound DID that doesn't have a specific route — point it at your receptionist or main ring group.

Then add DID-specific routes

Create additional inbound routes for individual DIDs that need specific routing.

Step 6 — Per-Extension Caller ID (DOD)

To assign different outbound caller IDs to different extensions using Direct Outward Dialling (DOD):

1. Navigate to Extension/Trunk → VoIP Trunks
2. Click your Simtex-SIP trunk to edit it
3. Click + Add DOD
4. Enter the DOD Number (one of your DIDs in E.164 format)
5. Enter a DOD Name (friendly label)
6. Select the Available Extensions that should use this DOD number
7. Click Save, then Apply Changes

The DID must be allocated to your Simtex account — you cannot present arbitrary numbers.

Testing Your Trunk

Once configured, verify everything works:

1. Check trunk status — navigate to System Status → Dashboard and check the Trunks widget. A blue dot indicates the trunk is registered
2. Make an outbound call — dial an external number from an extension and confirm two-way audio
3. Receive an inbound call — call one of your DIDs from a mobile and confirm it routes correctly
4. Verify caller ID — check your outbound caller ID displays correctly on the receiving end
5. Check voicemail — leave a voicemail to ensure DTMF tones are working correctly through the trunk

Security Hardening

After configuring your trunk, take these essential steps to secure your Grandstream UCM:

Change Default Credentials

If you haven't already, change the default admin password immediately. The factory default is admin / admin.

Firewall and Access Control

• Restrict web GUI access — use the UCM's built-in firewall rules to limit admin access to trusted IPs
• Disable unused protocols — turn off SSH, Telnet, and HTTP (use HTTPS only) if not needed
• SIP/RTP ports — ensure only the necessary SIP (5060) and RTP (10000-20000) ports are accessible

Additional security measures

• Strong extension passwords — use complex, auto-generated passwords for all extensions
• Firmware updates — keep your UCM firmware current via Maintenance → Upgrade
• Channel limits — keep Maximum Channels on the trunk set to your actual requirement
• Failover trunk — configure a failover trunk in outbound routes for resilience

Need Help?

If you run into any issues configuring your Grandstream UCM trunk, our support team can verify your trunk registration status from our side and assist with troubleshooting.

Contact Simtex Support