Block Inbound Calls

Overview and Benefits

Webex Calling customer administrators can block incoming PSTN calls from numbers that are either spam or harassing. You can configure policies for an organization to block calls from one of the following numbers:

• Configured numbers, for example: telemarketing callers or collection agencies
• Known offenders, such as disgruntled customers or ex-employees

Blocking these calls helps to reduce time in answering them and protect the users from security threats or harassment.

Webex Calling rejects an external (PSTN) call coming in from blocked numbers, which are defined in the call block list. The callers are disconnected without hearing any announcement from Webex Calling. The calling numbers (coming from the PSTN trunks) are matched against the locally configured E164 patterns that are configured in Control Hub.
For a successful match and call rejection, specify the calling number from the PSTN trunk in an equivalent E164 format. If the number schema used is non-E164, use the normalization rules at the Local gateway (for on-premise PSTN trunks) before sending the calls to Webex Calling.

Webex Calling can block calls in these scenarios:

• Calls from anonymous numbers where the calling information isn’t available in the SIP From/P-Asserted-Id headers.
• Calls with the presentation status marked as private. (The Privacy header is marked as id).

Please Note: Even though blocked contacts won’t be able to call you, you can still make an outbound call to the blocked numbers.

Creation

To create a block list with numbers that can’t make incoming calls to your organization:

1. From Control Hub, go to Services and click Calling.
2. Go to Service settings and scroll down to Call Block List.
3. Add or remove phone numbers, country codes, or other patterns to the call block list. Ensure that the numbers and patterns are in E164 format.

Click image for large view

• Block calls with no caller ID— blocks incoming calls from PSTN without calling line information (Caller ID).
• Block calls from hidden private numbers— blocks all calls from callers with private numbers or hidden identities.

4. Select Add to add numbers or patterns to block from calling the user's organization.

Follow these guidelines for adding numbers or patterns:

• Enter patterns in E164 format.
• Wildcards include the use of “!” representing a sequence of one or more digits.
• “X” represents a single number (0-9).

5. You can add up to 200 numbers or patterns per organization. To add numbers in bulk, select Import CSV.

Numbers and patterns added to the block list are visible above the input field. Each number is validated as you enter them.
When you don’t enter any blocked numbers, a notification stating that there are no current blocked numbers added to this customer organization displays.
           

6. Click Save to save the number. To remove a number, select “X”. Save is enabled after entering the first valid number.

7. Click Delete to delete an entry or Clear all to delete all numbers in the block list. A notification displays to confirm the action.

Troubleshooting

To troubleshoot issues with blocking inbound spam calls, follow these steps.
 If the functionality isn’t working, use the potential workarounds or solutions to resolve the issue.

Issue: Webex Calling doesn’t block incoming PSTN calls, although the numbers are configured in the Call Block List.

Workaround/Resolution

1. Check the configured patterns in the Control Hub under Call Block List.

• Ensure that the E164 number pattern exactly matches the calling number that you’re trying to block.
• When using a wildcard pattern X, the number of digits must match the number of X characters you’ve configured.

If you want to block all numbers coming in from NPA-NXX 212-505, use an E164 format of +1212505XXXX.

2. Check on the use of E164 numbering formats. If using National numbering schemes, then deploy the normalization rules at the Local Gateway trunk before sending the incoming PSTN call to Webex Calling.
   A sample normalization rule (IOS-XE SIP Profile to transform the From Header into an E164 format) for reference:

• Incoming SIP INVITE (received at Local Gateway) over the incoming PSTN Trunk:
  INVITE sip:12125052000@https://10.1.1.7 SIP/2.0
  Via: SIP/2.0/UDP 12.254.48.7:5060;branch=z9hG4bK14fcef5a;rport
  Max-Forwards: 70
  From: sip:17326991000@12.254.48.7;tag=as3f62ecae
  To: sip:61295032222@103.97.170.3
  Contact: sip:17326991000@12.254.48.7:5060

• Normalized SIP INVITE (sent to Webex Calling) from LGW:
  INVITE sip:12125052000@https://10.1.1.7 SIP/2.0
  Via: SIP/2.0/UDP 12.254.48.7:5060;branch=z9hG4bK14fcef5a;rport
  Max-Forwards: 70
  From: sip:+17326991000@12.254.48.7;tag=as3f62ecae
  To: sip:61295032222@103.97.170.3
  Contact: sip:17326991000@12.254.48.7:5060

• SIP Profile applied on IOS-XE Dial peer towards Webex Calling:
  voice class sip-profiles 1
  request INVITE sip-header From modify "ip:17" "ip:+17"