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The CLI/ANI field is the From part of the SIP INVITE message. This contains specific information about the caller, particularly the name and number of the person attempting to contact a user in a VoIP system. This is more commonly known as "Caller ID" in standard phone systems.

Configure CLI

To set CLI options:

  1. Click on the + button.
  2. Fill out the fields in the dialogue box and Save.

Field details:

  • Force CLI: To change the CLI that is presented for another, enter the CLI you wish to present, and click the Force CLI box. It will allow you to override the previous number with one that is accepted. You can add a whitelist of CLIs and select Force on a CLI which you wish to be used if none of the others in the whitelist match.

  • Rewrite CLI: A CLI can be re-written. For example, you can add 123456789 in the CLI box, and then rewrite by adding 987654321 in the re-write CLI box. (See Advanced CLI Match and Manipulation below.)

  • P-Asserted-ID: P-Asserted-Identification is another SIP Header. It is not presented but allows telephone companies to identify originators on a network-only level. A P-Asserted-ID uses the same syntax as Replace CLI.

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Advanced CLI Match & Manipulation

The CLI system uses Regular Expressions to match and replace numbers. Here are a few examples:

CLI Replace CLI Description
123456789 ^1234 Allows only numbers starting with 1234 to pass
123456789 789$ Allows only numbers ending with 789 to pass
12345678912 ^[0-9]{11,12}$ Allows only numbers with 11 or 12 digits to pass
+123456789 ^+([0-9]+)$ \1 Remove leading +
01782123456 ^0([1-9]+)$ 44\1 Remove leading 0 and replace with 44

To learn more about writing regular expressions, visit for tutorials and exercises available for all levels of expertise.


Whitelisted CLIs are those that allowed to pass through the system. This is added in the Customer Card:

  1. Go to Management > Customer
  2. Click the [customer] > Routing
  3. Under CLI, click on the + button.
  4. Enter the number in the CLI field then click Save

CLI Restrict

CLI Restrict lets you block calls. The blocked CLI is added in the Provider Rate Card:

  1. Click Management > Rate Card.
  2. Select Provider Rate Card (under the Name column).
  3. Select Properties > Advanced.
  4. Enter the CLI/ANIs you want to block in the CLI Restrict box.
  5. Click Save.

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General Condition 6 (GC6) Compliance

ConnexCS is GC6 compliant for end users, which

requires Communications Providers (CPs) to provide CLI facilities, and ensure that the CLI Data provided with a call includes a valid, dialable telephone number which uniquely identifies the caller." For details on this General Condition, including guidelines for "valid" and "dialable" numbers, see Ofcom's Guidance on CLI Facilities.

To configure per customer, set the CLI P-Asserted-ID found in the customer routing configuration.