# Configure DID Numbers on a Trunk

Most of the time you assign DID (Direct Inward Dialing) numbers to inbound routes so that calls can be steered by the number the caller dialed. In a few situations, though, the DID numbers need to live on the trunk itself. This page explains those situations and walks through adding and deleting DID numbers on a trunk.

:::note
DID (Direct Inward Dialing) and DDI (Direct Dialing In) are two names for the same thing: a phone number your provider routes to your system so outside callers can reach you. DDI is the term used in Europe and the UK. The portal labels the field **DID/DDI**, so treat the two as interchangeable.
:::

## When to configure DIDs on a trunk

There are two common reasons to attach DID numbers directly to a trunk:

- **SIP register trunks with mismatched credentials.** On a SIP (Session Initiation Protocol) register trunk, if your ITSP (Internet Telephony Service Provider, the company that supplies your phone service) issues DID numbers that differ from the trunk's SIP authentication name, you must list those numbers on the trunk.
- **Telling inbound calls apart.** Pairing each DID number with a descriptive name lets you recognize at a glance which number a caller dialed.

:::caution
For a SIP register trunk where the provided DID numbers do not match the SIP authentication name, adding the DID numbers to the trunk is not optional. If you skip it, every inbound call arriving over that trunk is rejected.
:::

For the more typical case of routing calls by the dialed number, see [Route Inbound Calls based on DID Numbers](/pbx/administrator-guide/route-inbound-calls-based-on-did-numbers/).

## Before you start

Buy the DID numbers you plan to use from your trunk provider. You can only add numbers here that the provider has already assigned to you.

## Add a DID number

1. Sign in to your Cloud Voice PBX (Private Branch Exchange, your phone system) portal and go to **Extension and Trunk > Trunk**, then open the trunk you want to edit.
2. Select the **DIDs/DDIs** tab.
3. Click **Add** and enter your numbers using one of the following methods.

   To add a single number:

   1. Set **Create Method** to **Single DID**.
   2. Fill in the fields:
      - **DID/DDI**: Type the number supplied by your provider.
      - **DID/DDI Name** (optional): Give the number a label to help you distinguish calls by DID. When someone dials this number, the label appears on the called party's device.

   To add a block of consecutive numbers:

   1. Set **Create Method** to **DID Range**.
   2. Fill in the fields:
      - **DID Range**: Enter the first and last number in the range.
      - **DID/DDI Name** (optional): Give the range a label to help you distinguish calls by DID. When one of these numbers is dialed, the label appears on the called party's device.

4. Click **Confirm**.
5. Click **Save**, then **Apply**.

:::tip
Set a **DID/DDI Name** whenever you have more than one number on a trunk. The name shows on the answering phone, so staff can tell instantly whether a call came in on the sales line, the support line, or a personal number without checking the dialed digits.
:::

:::tip
Use **DID Range** when your provider hands you a solid block of consecutive numbers. It saves you from adding them one at a time. If your numbers are not consecutive, add each one with **Single DID**.
:::

:::caution
Your changes are not live until you click **Apply**. Saving alone stores the configuration but does not activate it, so inbound routing keeps using the old settings until you apply.
:::

## Delete DID numbers

1. Sign in to your Cloud Voice PBX portal and go to **Extension and Trunk > Trunk**, then open the trunk you want to edit.
2. Select the **DIDs/DDIs** tab.
3. To remove a single number, click ![Delete a DID number](/images/pbx/delete.png) next to it.
4. To remove several at once, tick the checkbox beside each number and click **Delete**.
5. Click **Save**.

:::caution
Removing a DID number that inbound calls depend on will break those calls. On a SIP register trunk with mismatched credentials, deleting a needed number causes calls to that number to fail. Confirm the number is no longer in use on any inbound route before you delete it.
:::