Cisco Unified SRST Administration Guide (All Versions) - Cisco Unified SRST Feature Overview

Publisher

Cisco Systems

URL

https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cusrst/admin/sccp_sip_srst/configuration/guide/SCCP_and_SIP_SRST_Admin_Guide/srst_overview.html

Published

2026-04-25

Updated

unknown

Accessed

2026-09-24

HTTP status

200

License

Cisco documentation; all rights reserved; no-redistribution; short excerpts and locators only

Source notes citing this source

• TLS version 1.3 is not supported for the Webex Survivability Gateway operating mode. in context
• If a phone already has an active standby connection to the SRST router, fallback takes 10 to 20 seconds after it loses Unified CM. in context
• Cisco Unified SRST lets a branch router handle calls for Cisco IP phones that have lost connection to their primary, secondary and tertiary Unified CM nodes. in context
• During SCCP SRST operation the MeetMe, GPickUp, Park and Confrn function keys are dimmed because SRST does not support them. in context
• Starting with Cisco IOS XE 17.9.3 and Dublin 17.11.1a, a Survivability Gateway configuration and a Unified SRST configuration can run together on the same gateway. in context
• Enabling Cisco Unified SIP SRST requires an SRST feature license. in context
• Secure SRST supports TLS 1.3 starting with Unified SRST 14.4 (IOS XE 17.14.1a), in addition to TLS 1.0, 1.1 and 1.2. in context
• SRST fallback detection typically takes three times the keepalive period (30-second default), while phones holding a standby connection to SRST fall back in about 10 to 20 seconds. in context
• Under Unified SRST, IP phones that stop receiving keepalives from Unified CM register with the local SRST router, which activates automatically and builds a local database of the phones. in context
• A phone in SRST fallback cannot re-establish its connection to the primary Unified CM while it is on an active call. in context
• In SRST mode, phones periodically try to reconnect to Unified CM, by default every 120 seconds (Connection Monitor Duration), and cancel their SRST registration automatically once reconnected. in context
• In SRST fallback, MeetMe, group pickup, park and conference are unavailable on the phone, and SIP SRST does not support BLF speed-dial notification, call-forward-all synchronisation, directory services or music on hold. in context

Cite this source record

APA

WarmTransfer. (2026, April 25). Cisco Unified SRST Administration Guide (All Versions) - Cisco Unified SRST Feature Overview. WarmTransfer. https://warmtransfer.net/knowledge/sources/cisco-srst-admin-feature-overview

BibTeX

@misc{warmtransfer-cisco-srst-admin-feature-overview,
  title  = {Cisco Unified SRST Administration Guide (All Versions) - Cisco Unified SRST Feature Overview},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/sources/cisco-srst-admin-feature-overview},
  note   = {Cisco Systems, accessed 2026-09-24}
}