Cisco Systems OL-14619-01 manual 6-20, 11 Cisco Unified Communications Manager Fallback with PSTN

Chapter 6 Integrating Cisco Unity with the Phone System

Integrating with Cisco Unified Communications Manager Express (by Using SCCP or SIP)

Figure 6-10 Cisco Unified Communications Manager Fallback with BRI or PRI

IP	SRST Gateway	CM Gateway
		BRI/PRI

IP

WAN Failure

IP

Cisco CallManager

WAN

Voice-Mail Server

88981

When the WAN is down and Cisco Unity has foreign exchange office (FXO) or foreign exchange station (FXS) access connect to a public switched telephone network (PSTN), Cisco Unity uses in-band dual tone multifrequency (DTMF) signaling (see Figure 6-11).

Figure 6-11 Cisco Unified Communications Manager Fallback with PSTN

IP		Cisco CallManager gateway
	FXS	FXO
		PSTN

IP

WAN failure

IP

WAN

Voice-mail server

Cisco CallManager

88980

In both configurations, phone message buttons remain active and calls to busy or unanswered numbers are forwarded to Cisco Unity. The installer must configure access from the dial peers to the voice-mail system, and establish routing to Cisco Unity for busy and unanswered calls and for the message button.

If Cisco Unity is accessed over FXO or FXS, you must configure instructions (DTMF patterns) for Cisco Unity so it can access the correct voice-mail system mailbox.

When using Cisco Unified SRST with Cisco Unity, the integration has the following limitations during a WAN outage:

Call forward to busy greeting

When the Cisco Unified SRST router uses FXO/FXS connections to the PSTN and a call is forwarded from a branch office to Cisco Unity, the busy greeting cannot play.

	Design Guide for Cisco Unity Release 5.x
6-20	OL-14619-01