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SRST Support for SIP phones

You can use SIP SRST for SIP  IP phones.

Cisco Unified SIP SRST provides backup to an external SIP proxy server by  providing basic registrar and redirect server or back-to-back user agent (B2BUA)  services. These services are used by a SIP IP phone in the event of a WAN  connection outage when the SIP phone is unable to communicate with its primary  SIP proxy.

Cisco Unified SIP SRST can support SIP phones with standard  RFC 3261 feature support locally and across SIP WAN networks. With Cisco Unified  SIP SRST, SIP phones can place calls across SIP networks in the same way as SCCP  phones.

Cisco Unified SIP SRST supports the following call combinations:

  • SIP phone to SIP phone
  • SIP phone to PSTN / router voice-port
  • SIP phone to Skinny Client Control Protocol (SCCP) phone
  • SIP phone to WAN VoIP using SIP

For more information, refer the following documents: