# DID Number to Specific Extension Parameters

When an inbound route matches each DID (Direct Inward Dialing) number to a single extension, you can move those mappings in and out of Cloud Voice as a CSV (comma-separated values) file. This reference explains every column that appears in that file so you can fill it in correctly before importing, or interpret it after an export.

Each row pairs one DID number with the extension that should answer calls to it.

| Column | What it holds | Required | Rules | Default |
| --- | --- | --- | --- | --- |
| DID Number | The exact number that Cloud Voice compares against the dialed (callee) number. A call is only sent down this inbound route when the number the caller dialed matches this DID. | Yes, when the route's DID Matching Mode is `pattern_to_ext_list`. | 31 characters maximum. Only digits, letters, and the characters `(` `)` `.` `-` `+` `*` `#` are accepted. | N/A |
| Extension Matched | The extension that receives calls placed to the DID in the same row. The relationship is one-to-one: each DID routes to exactly one extension. | Yes, when the route's DID Matching Mode is `pattern_to_ext_list`. | Must be an existing extension number. | N/A |

:::note
Both columns are only meaningful when the inbound route uses the `pattern_to_ext_list` DID Matching Mode. If the route uses a different mode, these values are ignored.
:::

:::caution
The match is exact: a call only follows this route when the callee number equals the DID Number value, digit for digit. If the format you enter (for example, with or without a leading `+` or country code) does not match what your carrier actually delivers, calls to that number will not route. Confirm the delivered number before importing.
:::