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This chapter is from the book

SRST and E-SRST Configuration

As explained in the previous section, SRST and E-SRST are the two possible ways to provide call control redundancy for the remote sites. This section details the configuration for the these two scenarios.

Example 5-1 outlines SRST configuration.

Example 5-1 SRST Configuration

SRST-Router(config)# call-manager-fallback
SRST-Router(config-cm-fallback)# ip source-address port 2000
SRST-Router(config-cm-fallback)# max-ephones 10
SRST-Router(config-cm-fallback)# max-dn 100
SRST-Router(config-cm-fallback)# max-conferences 4 gain -6
SRST-Router(config-cm-fallback)# transfer-system full-consult
SRST-Router(config-cm-fallback)# secondary-dialtone 9
SRST-Router(config-cm-fallback)# moh music-on-hold.au
SRST-Router(config-cm-fallback)# time-format 24
SRST-Router(config-cm-fallback)# date-format dd-mm-yy
SRST-Router(config-cm-fallback)# system message SRST Mode

Example 5-1 defines IOS commands that help configure SRST on Cisco IOS router. The key commands are as follows:

  • ip source-address defines the address of a physical or virtual (loopback) interface on the router with which the phones should register while using the SRST process. This is defined along with a port (2000 for SCCP).
  • max-ephones defines the total number of ephones, and max-dn defines the maximum number of directory numbers under call-manager-fallback for the phones at the remote site.
  • secondary-dialtone gives the same dialing experience for plain switched telephone network (PSTN) calls to end users (as they would experience when phones are registered with CUCM). In Example 5-1, pressing 9 gives an outside dialtone (it can be set to 0 for Europe and other regions as required).
  • moh (music on hold) command defines the filename that is used for music on hold. This in turn allows playing MOH when remote site is in SRST mode.
  • time and date format set the right format for the phones.
  • system message helps display a message (configurable by administrator) that can help make users aware that the endpoints are running in SRST mode.

Example 5-2 explains Cisco Unified CME based SCCP based E-SRST.

Example 5-2 SCCP E-SRST Configuration

CUCME-Router(config)# telephony-service
CUCME-Router(config-telephony)# srst mode auto-provision none
CUCME-Router(config-telephony)# srst dn line-mode dual
CUCME-Router(config-telephony)# srst ephone template 1
CUCME-Router(config-telephony)# srst dn template 1
CUCME-Router(config-telephony)# max-ephone 20
CUCME-Router(config-telephony)# max-dn 40
CUCME-Router(config-telephony)# ip source-address port 2000
CUCME-Router(config-telephony)# moh music-on-hold.au
CUCME-Router(config-telephony)# max-conferences 4 gain -6
CUCME-Router(config-telephony)# secondary-dialtone 9
CUCME-Router(config-telephony)# system message SRST Mode
CUCME-Router(config)# ephone-template 1
CUCME-Router(config-ephone-template)# keep-conference local-only
CUCME-Router(config)# ephone-dn-template 1
CUCME-Router(config-ephone-template)# hold-alert 25 idle

Example 5-2 has a number of IOS commands that define the following tasks:

  • telephony-service initiates Cisco Unified CME configuration.
  • srst command before usual Cisco Unified CME commands defines Cisco Unified CME mode for E-SRST provisioning.
  • The mode for ephone-dns is set to dual-line.
  • ephone-template applies common ephone configuration for any newly configured phone on Cisco Unified CME in SRST mode.
  • dn template refers to the template used for defining common properties for a DN for a new ephone configured.

Other options are similar to traditional SRST configuration, as discussed earlier in Example 5-1.

Example 5-3 describes the configuration for Cisco Unified CME based SIP SRST.

Example 5-3 SIP E-SRST Configuration

CUCME-Router(config)# voice register global
CUCME-Router(config-register-global)# mode srst
CUCME-Router(config-register-global)# source-address port 5060
CUCME-Router(config-register-global)# max-dn 40
CUCME-Router(config-register-global)# max-pool 10
CUCME-Router(config- register-global)# system message SRST Mode

As shown in Example 5-3, the following commands help define various tasks:

  • SIP configuration starts with change of mode from cme to srst.
  • max-dn defines the maximum directory numbers (DNs) to be supported during SRST.
  • max-pool defines the maximum number of SIP voice register pools.
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