Enabling Fallback to Cisco Unified SRST for Call Control on Analog (FXS) Ports

First Published: June 27, 2005

Last Updated: November 26, 2012

 

This chapter describes how to enable remote Cisco Unified Communications Manager servers and the local Cisco Unified Survivable Remote Site Telephony (Cisco Unified SRST) router for determining the order in which the systems assume call control for analog endpoints connected to analog Foreign Exchange Station (FXS) ports on a Cisco voice gateway. Cisco Unified SRST provides fallback for analog endpoints in Cisco Unified Communications Manager only.

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Contents

Prerequisites for Enabling Fallback to Cisco Unified SRST for Call Control on Analog FXS Ports

Cisco IOS Gateway

  • The Cisco voice gateway must be set up and configured for operation. For information, see the appropriate Cisco configuration documentation.
  • SCCP is enabled on the Cisco voice gateway. For configuration information, see the “Enabling SCCP on the Voice Gateway” section.
  • Before Cisco IOS 15.0(1)M: To ensure that the analog phones can register in Cisco Unified SRST when required, such as when the Cisco VG224 is rebooted while Cisco Unified Communications Manager is in fallback mode, the DNs for analog phones connected to FXS ports on the Cisco voice gateway and registered in Cisco Unified Communications Manager must be explicitly configured on the Cisco VG224 using the station-id number command in voice-port configuration mode. For information, see the Cisco IOS Voice Command Reference.
note.gif

Noteblank.gif In Cisco IOS Release 15.0(1)M and later releases: When a directory number for an analog phone is added or changed in Cisco Unified Communications Manager, the station-id number command in voice-port configuration mode is automatically added for the new or modified directory number. Every time the Cisco VG224 receives DNs from Cisco Unified Communications Manager during registration, it checks the new DNs against the already-saved DNs. If at least one DN is different, then a background save is triggered and the DN is saved in the station-id number configuration. If the Cisco VG224 must register to Cisco Unified SRST after rebooting, it uses the saved DN to register the corresponding analog phone in Cisco Unified SRST.

Cisco Unified SRST

  • For Cisco SRST 3.3: Cisco IOS Release 12.3(14)T or a later release.
  • For Cisco SRST 3.4 and Cisco Unified SRST 4.0: Cisco IOS Release 12.4(2)T or a later release.

Cisco Unified Communications Manager

  • This document does not contain details about configuring Cisco Unified Communications Manager or Cisco Unified CME. See the documentation for these products for installation and configuration instructions.

Restrictions for Enabling Fallback to Cisco Unified SRST for Call Control on Analog FXS Ports

  • Switchover and switchback are supported using the graceful method only. Other switchover and switchback methods are not supported.
  • Cisco Unified SRST supports basic calls only; it does not support supplementary features.
  • Cisco Unified SRST does not provide fallback for analog endpoints in Cisco Unified Communications Manager Express (Cisco Unified CME).
  • In an actual Cisco Unified SRST scenario, when a Cisco Unified IP phone registers with a Cisco Unified CM, the Cisco Unified CM pushes Cisco Unified SRST information (using the selected device pool) to the Cisco Unified IP phone and the phone stores the information. However, in the case of an analog phone connected to Cisco IOS SCCP voice gateways, like the VG224, that provision is not available. These voice gateways do not perform autoconfiguration through the TFTP download of XML configuration files. The ports of these voice gateways do not receive or store any Cisco Unified SRST information from Cisco Unified CM so selective fallback is not possible with VG224 and similar voice gateway ports.

How to Enable Fallback to Cisco Unified SRST for Call Control on Analog FXS Ports

To assign priority levels to remote Cisco Unified Communications Manager servers and the local Cisco Unified SRST router for determining the order in which the systems assume call control if one becomes unavailable, perform the following steps.

SUMMARY STEPS

1.blank.gif enable

2.blank.gif configure terminal

3.blank.gif sccp ccm group group-number

4.blank.gif associate ccm identifier-number priority priority-number

5.blank.gif switchover method { graceful | immediate }

6.blank.gif switchback method { graceful | guard [ guard-timeout ] | immediate | uptime uptime-timeout }

7.blank.gif end

DETAILED STEPS

Command or Action
Purpose

Step 1

enable

 

Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

 

Router# configure terminal

Enters global configuration mode.

Step 3

sccp ccm group group-number

 

Router(config)# sccp ccm group 1

Creates a Cisco Unified Communications Manager and Cisco Unified SRST group and enters SCCP ccm configuration mode.

  • group-number —Number that identifies the group. Range: 1 to 65535.

Step 4

associate ccm identifier-number priority priority-number

 

Router(config-sccp-ccm)# associate ccm 10 priority 1

Adds a Cisco Unified Communications Manager server or Cisco Unified SRST router to the group and establishes its priority within the group.

  • identifier-number —Number that identifies the Cisco Unified Communications Manager server or Cisco Unified SRST router. This is the number that was assigned with the sccp ccm command. See the “Enabling SCCP on the Voice Gateway” section.
  • priority priority-number —Number that indicates the priority of this Cisco Unified Communications Manager server or Cisco Unified SRST router. Range: 1 to 4, where 1 is the highest priority. Assign the lowest priority to Cisco Unified SRST.

Note A second Cisco Unified Communications Manager server that is entered with a lower priority number becomes a backup system.

Step 5

switchover method { graceful | immediate }

 

Router(config-sccp-ccm)# switchover method graceful

(Optional) Sets the switchover method that the voice gateway uses if connectivity to the primary Cisco Unified Communications Manager fails.

  • graceful —Switchover happens only after all active sessions are terminated gracefully. This is the only supported method.
  • immediate —Switchover to a secondary call-control system happens immediately regardless of whether or not there are active connections.

Note The switchover method graceful command is enabled by default. Other switchover methods are not supported.

Step 6

switchback method { graceful | guard [ guard-timeout ] | immediate | uptime uptime-timeout }

 

Router(config-sccp-ccm)# switchback method graceful

Sets the switchback method that the voice gateway uses when the primary or higher priority Cisco Unified Communications Manager becomes available again.

  • graceful —Switchback happens only after all active sessions are terminated gracefully. This is the only supported method.

Note The switchback method graceful command must be enabled. Other switchback methods are not supported.

Step 7

end

 

Router(config-sccp-ccm)# end

Exits SCCP ccm configuration mode and returns to privileged EXEC mode.

Configuration Examples for SCCP and the STC Application

The following example enables SCCP communication on Fast Ethernet interface 0/0 to two Cisco Unified Communications Manager servers and a Cisco Unified SRST router. In SCCP group 1, the Cisco Unified Communications Manager server at IP address 10.4.13.20 is assigned priority 1, making it the primary call-control system. If connectivity to the primary fails, call control reverts to the backup Cisco Unified Communications Manager server at 10.4.13.70. If connectivity to both Cisco Unified Communications Manager servers fails, call control reverts to the Cisco Unified SRST router at 10.4.18.40.

Gateway# show running-config
.
.
.
sccp local FastEthernet0/0
sccp ccm 10.4.13.20 identifier 10
sccp ccm 10.4.13.70 identifier 12
sccp ccm 172.16.10.40 identifier 30
sccp
!
sccp ccm group 1
associate ccm 10 priority 1
associate ccm 12 priority 2
associate ccm 30 priority 3
switchback method graceful
!
!

Additional References

The following sections provide references related to SCCP analog phone support for FXS ports on the Cisco voice gateway.

Related Documents

Related Topic
Document Title

Cisco Unified Communications Manager

Cisco Unified Communications Manager documentation

Cisco Unified Communications Manager Express

Cisco Unified Communications Manager Express documentation

Cisco IOS debugging

Cisco IOS Debug Command Reference

Cisco IOS voice commands

Cisco IOS Voice Command Reference

Cisco IOS voice configuration

Cisco IOS Voice Configuration Library

Cisco voice gateway

Conferencing and transcoding resources

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