CCIE Voice Lab Preparation Notes #2

SRST
There are four SRST scenarios:

• SRST configuration for MGCP gateways
• SRST for H.323 gateways
• SRST for SIP gateways
• SRST on CME

1. MGCP Gateway

• Enables fallback for MGCP gateway
  router(config)#ccm-manager fallback-mgcp
• Enters SRST configuration mode
  router(config)#call-manager-fallback
• Configure Basic SRST settings
  router(config-cm-fallback)#max-dn value [dual-line] [preference preference-order]
  router(config-cm-fallback)#max-ephone value
  router(config-cm-fallback)#ip source-address ip-address
  router(config-cm-fallback)#system message primary message
  router(config-cm-fallback)#user-local country-code
  router(config-cm-fallback)#time-format [12|24]
  router(config-cm-fallback)#date-format format
  router(config-cm-fallback)#moh filename
  router(config-cm-fallback)#max-conferences value
  router(config-cm-fallback)#call-forward reason number
  router(config-cm-fallback)#voicemail number
  router(config-cm-fallback)#secondary-dialtone digit-string
• Configure the MGCP gateway as SRST reference in CUCM.
• Assign the SRST reference to IP phones by configuring corresponding device pool.
• The last step is to configure H.323 incoming and outgoing dial peers for SRST.
  

Additionally, you can use the router to provide multicast MOH to IP phones.

router(config)#ccm-manager music-on-hold

router(config)#call-manager-fallback

router(config-cm-fallback)#moh filename

router(config-cm-fallback)#multicast moh multicast-address route address-to-send-packets-to

2. SRST for H.323

On H.323 gateways, when the WAN link fails, active calls from Cisco Unified IP phones to PSTN are not maintained by default. Call preservation may work with 'no h225 timeout keepalive' command under 'voice service voip' 'h323' configuration mode.

3. SRST for SIP Gateway

SIP SRST feature is using Back-to-Back User Agent Mode.

By default, when configuring 'voice register global', it is SRST mode.

4. SRST on CME

router(config)#telephony-service

router(config-telephony)#srst mode auto-provision {all|dn|none}

Use none when configuring SRST with CUCM.