Call Limitations

This section explains the limitations and observations in the looping dial plan with the proposed solutions.

Call Type

Observation

Proposed Solution

Incoming calls from PSTN forwarded via:

  • Call Forward All back to the PSTN

  • Call Forward All, No Answer, …To VoiceMail

  • SNR

  • Dial Via Office

For any such call types or features, creating an outbound Call Leg based on the restricted A -

Number by Cisco Unified CM, fails if the incoming calling party is anonymous. In this scenario, the calling party number does not have a PAI field and the From field is set to “anonymous” with no digits in the incoming CLIR PSTN call. For security purposes, HCS prefixes a dial plan pattern (for example, +*+*) to the incoming calling party number to “anonymous”.

If the Cisco Unified CM pattern does not have the capability of that matching letter (dial plan pattern), the call fails. Also, Cisco Unified CM cannot match the dial plan pattern (for example, +*+*) because the calling party number (“+*+*anonymous”) is treated as enbloc by Cisco Unified CM.

Insert a dummy PAI in Cisco Unified CM with a Lua script.

  • INBOUND: If there is no P-Asserted-Identity (PAID), set the PAID to <customer-defined-dummy-DN> and set the privacy to restrict the number.

  • OUTBOUND: If the PAID is <customer-defined-dummy-DN>, remove the PAID

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PSTN Access Prefix

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Business Admin Portal Guide