====== CUCME SRST ======
  * A more feature rich fallback technology
  * Supports features like hunt groups or Call Park
  * Allows access to Cisco Unity Voice-mail boxes using SCCP
  * Supports automatic SRST configuration of SCCP phones
  * Supports preconfigured phones with features assigned
  * Supports a max of 240 SCCP IP phones
  * Doesn't support Cisco VG248 Analog Phone Gateway
  * Doesn't support secure voice using SRTP
  * Doesn't support SIP phone failover

===== Configuration Mode =====
  * SNAP
    * Allows phones and directory numbers to be learn automatically
  * Allows a mix of preconfigured phones and directory numbers and phones directory numbers learned by SNAP
    * Only those phones and directory numbers that required individual configuration needs to be preconfigured.
    * Preconfiguration can be based on MAC address or on directory number.
    * Phones that do not required individual settings do not have to be preconfigured.
{{cucm-csrst1.png|}}

===== Registration Process =====
  * When an IP phone registers to CUCME during SRST:
  * The router searches for an existing ephone with the MAC address of the phone.
    * If found, the ephone needs to be configured with a directory number (button command), or auto assignment has to be enabled
    * If not found, the router searches for an existing ephone-dn that matches the IP phone directory number (learned by SNAP).
      * If found, an ephone is added that refers to the matched ephone-dn.
      * If not found, an ephone is added that refers to a newly created ephone-dn autoconfigured by SNAP.
  * Whenever an ephone is added by SRST, the srst ephone template is applied.
  * Whenever an ephone-dn is added by SRST, the srst ephone-dn template is applied.

===== Configuration =====

==== CUCME ====
  * Configure [[..ccme:ccme-sccp|CUCME]]

==== CUCME SRST ====
  * Enable SRST mode
    * all - writes info learned ephones and ephone-dn into the running config
    * dn - writes info learned ephone-dn into running config
    * none - does not include info learned into running config
  * Specifies the line mode for ephone-dn. Default is single line.
  * Specifies a description
<code>
telephony-service
  srst mode auto-provision {all | dn | none}
  srst dn line-mode {dual | single}
  srst dn template <1-15>
  srst ephone description <string>
</code>

  * Specifies an ephone template
<code>
ephone-template 1
  keep-conference local-only
!
telephony-service
  srst ephone template 1  
</code>

  * Specifies an ephone-dn template
<code>
ephone-dn-template 3
  hold-alert 25 idle
!
telephony-service
  srst dn template 1 3
</code>