Customer Trunks

A Customer Trunk is the connection your customer's own phone system uses to connect into UCBC — the opposite direction from a carrier trunk. Where a Trunk ITSP/Gateway connects you outward to your telephone carrier, a Customer Trunk is how one of your customers' own PBX systems (or their Microsoft Teams phone system) connects inward to you.

This is only available on trunk-type customer accounts (domains set up to act as a SIP trunk customer, not a standard hosted-extensions account).

Overview#

Customer Trunks has four tabs:

• Trunks — the list of SIP trunk connections for this customer.
• IP Permissions — trusted IP addresses for this customer's own equipment.
• Call Detail Records — call history for this customer's trunk traffic.
• MS Trunk Cert — certificate setup and status for a Microsoft Teams Direct Routing trunk.

A customer can have more than one trunk (for example, a primary connection plus a backup). Exactly one trunk per customer is marked Primary — it's the one inbound numbers assigned to that customer are delivered to automatically.

There are two trunk types:

• Standard Trunk — a normal SIP trunk to the customer's own PBX.
• MS Teams Trunk — connects instead to the customer's Microsoft Teams Phone System, using Microsoft's Direct Routing protocol.

The Customer Trunks list

Screenshot needed · customer-trunks-list

How to Create a Customer Trunk#

Standard Trunk#

1. Go to Customer Trunks and click Add.
2. Enter a Trunk Name.
3. Leave Trunk Type as Standard Trunk.
4. Set Register:
   • True — the customer's PBX registers to you with a username/password (use this when the customer has no static IP address). An Identifier and Password are auto-generated for you; double-click either field if you need to set a custom value.
   • False — the customer has a static IP address you trust directly. Enter their address under Proxy (add a port if needed, e.g. 203.0.113.5:5080; defaults to port 5060).
5. Optionally set Channels (maximum simultaneous calls on this trunk; 0 = unlimited) and Codec Preferences.
6. If Register is True, you may set fallback Outbound Caller ID Name/Number — used only when the customer's device sends no caller ID of its own; it never overrides a real per-call caller ID.
7. If this is the customer's only trunk, it's automatically Primary. Otherwise choose whether it should become the Primary trunk.
8. Make sure Enabled is True and click Save.

MS Teams Trunk#

1. Click Add, then set Trunk Type to MS Teams Trunk.
2. The SBC FQDN for this trunk is generated automatically — this is the exact address you'll give the customer to enter as their PSTN Gateway address in their own Microsoft Teams admin center. (You can double-click it to adjust before saving if needed.)
3. Optionally record the customer's Teams Tenant Domain (e.g. contoso.onmicrosoft.com) for your own reference — it isn't used in call routing.
4. Set Channels — this becomes Microsoft's maximum concurrent call setting for this connection, and must be at least 1 (Microsoft has no "unlimited" option).
5. Save, then open the MS Trunk Cert tab to finish setup (see below). An in-app step-by-step connection guide is also linked from both this form and the MS Trunk Cert tab.

Completing MS Teams trunk setup (MS Trunk Cert tab)

Microsoft requires every Direct Routing connection to present a valid SSL certificate from a specific list of accepted providers — Let's Encrypt is not accepted. You have two options:

• Get Certificate Automatically — one click; requests, installs, and automatically renews a certificate before it expires, using this platform's own configured certificate account (see SBC > ACME Settings). Requires DNS for the SBC FQDN to already resolve to this platform's address.
• Upload Your Own — if you'd rather bring a certificate from a different accepted provider, upload the certificate file, its private key, and (if separate) the intermediate chain file.

The tab also shows Certificate Status (pending / active / expired / mismatch), the certificate's common name, issuer, and expiration date once one is installed.

Before a Teams trunk can carry real traffic, each Teams user also needs Phone System licensing on the customer's Microsoft 365 side, and the trunk must be registered as a PSTN Gateway in the customer's own Teams admin center — see the in-app guide for the full walkthrough.

How to Edit a Customer Trunk#

• Click the trunk's name to open its edit form and change any field, then save.
• From the trunk list you can also, without opening the form:
  • Toggle Enabled — turns the whole trunk on or off.
  • Toggle Register — switches between password-based and IP-based mode (Standard trunks only); your previous settings for whichever mode you switch away from are kept, so switching back doesn't lose anything.
  • Set Primary — makes a secondary trunk the primary one (automatically demotes the current primary).
  • Stop — immediately disconnects the trunk (useful for a non-paying or cancelled customer) without waiting for a registration to expire naturally.
  • Start / Retry — re-enables the trunk, or forces a fresh connection attempt.

How to Delete a Customer Trunk#

1. Go to Customer Trunks > Trunks.
2. Select the checkbox next to the trunk(s) to remove.
3. Click Delete and confirm.

Deleting a trunk removes its underlying connection details entirely (the registration identity or the IP-trust record, whichever applies).

IP Permissions Tab#

A trunk only works from an IP address listed here — this applies whether the trunk uses password registration or not. If a trunk is created but the customer's IP address isn't added here, the trunk cannot send or receive calls.

1. Go to Customer Trunks > IP Permissions, click Add.
2. Enter the customer's IP Address / CIDR (e.g. 102.223.20.174 or 102.223.20.0/24).
3. Add a description and save.
4. Toggle Enabled or delete entries from the list as needed.

Field Reference#

Customer Trunk#

IP Permission Entry#

MS Trunk Cert#

Tips & Common Issues#

• Trunk is enabled but can't send/receive calls: check IP Permissions — the customer's IP address must be listed there even if the trunk also uses password registration.
• Switching Register mode: your previous Identifier/Password or Proxy settings are preserved when you switch back, so you don't need to re-enter them each time.
• MS Teams trunk shows "No certificate uploaded yet": use Get Certificate Automatically on the MS Trunk Cert tab, or upload one from an accepted certificate authority — Let's Encrypt certificates are rejected by Microsoft.
• MS Teams calls connect with no audio: Microsoft requires encrypted media; a connect-with-no-audio symptom almost always points to a certificate or media-encryption mismatch, not a dialing problem.
• New MS Teams PSTN Gateway shows inactive right after setup: this can take anywhere from a few minutes to a day to fully propagate on Microsoft's side — this is normal, not a misconfiguration.
• Deleting the Primary trunk: another enabled trunk is automatically promoted to Primary so inbound numbers keep routing correctly.