1.22 Voice-Messaging Call Flows in SRST and AAR Mode

This topic shows the call flow when the WAN is unavailable or CAC blocks the call.

SRST and Cisco Unity Connection

  • The WAN is down and SRST takes over basic telephony.
  • Add alternate extensions (E.164 number) in Cisco Unity Connection.

When the WAN is unavailable, IP phones register with the SRST router. The figure shows how voice messaging is processed in SRST mode.

By default, there is no activity when a user presses the Messages button after the IP phones have registered with the SRST router. IP phones configured through the following commands can reach the mailbox in case of SRST fallback. Users can leave a message if the called user does not answer or is busy. The following commands need to be configured on the SRST router to offer voice messaging over PSTN as a backup during a WAN failure:

  • call-manager-fallback
  • voicemail 914083552300
  • call-forward busy 914083552300
  • call-forward noan 914083552300 timeout 5

When you dial out, voice translation rules on the voice gateway modify the calling number to the E.164 format for all Cisco Unity Connection users. Therefore, add the alternate number (E.164) for all Cisco Unity Connection users in the centralized voicemail system. Voice translation rules might also modify the redirected number, either outgoing or incoming.

AAR and Cisco Unity Connection

  • Hunt pilot for voicemail needs to be set up for AAR.
  • Redirecting numbers need to be transmitted; outgoing on remote router and incoming on main router.
  • AAR CSS on remote site router needs to be set.
  • Cisco Unity Connection user needs an alternate E.164 number to be configured.

When the WAN is busy and the AAR process takes over call processing, the AAR process rebuilds the voicemail number. This process combines the AAR group, external phone-number mask, and directory number; for example, 91 + 408355XXXX + 2300 = 914083552300. Be sure to configure the AAR CSS in the inbound call section on the remote gateway; otherwise, the calls will not be rerouted over the PSTN.

If a caller dials a remote phone via PSTN and the remote user does not answer, then the call is sent to the voice-messaging system via PSTN. The same behavior occurs if a user presses the Messages button. The redirected number must be sent in addition to the calling and called numbers. If the gateway configuration is not correct, the redirected number cannot be sent and the caller reaches the standard opening greeting.

If the redirected number is sent as an E.164 number, then configure an alternate extension on Cisco Unity Connection. For a call via the PSTN, the calling and redirected numbers are sent in E.164 format. Unless an alternate extension is configured, the standard opening greeting is played instead of the user greeting. Redirected numbers can be modified via voice translation rules.


Author: drbabbers

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