• 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

• 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.

• 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.

• Configure CUCME

• 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

telephony-service
  srst mode auto-provision {all | dn | none}
  srst dn line-mode {dual | single}
  srst dn template <1-15>
  srst ephone description <string>

• Specifies an ephone template

ephone-template 1
  keep-conference local-only
!
telephony-service
  srst ephone template 1  

• Specifies an ephone-dn template

ephone-dn-template 3
  hold-alert 25 idle
!
telephony-service
  srst dn template 1 3