T3
CUBE and SRST
Two legs, and the phone when CUCM is gone
Sources and go deeper
Opened 2026-10. A row marked confirm has no link, because that page was not verified.
- Cisco. Understand IOS and IOS XE call routing last checked 2026-10
- Cisco. CUBE configuration guide, dial peers (IOS XE 17.6 onwards) last checked 2026-10
- RFC. RFC 4733, RTP telephony events last checked 2026-10
- Cisco. Cisco Unified Border Element product support last checked 2026-10
- Protocol and ports. IANA SIP parameters last checked 2026-10
- Protocol and ports. IANA service names and port numbers last checked 2026-10
- Community. Cisco Community, Collaboration knowledge base last checked 2026-10
- Wikipedia. Session Initiation Protocol (Wikipedia) last checked 2026-10
- Wikipedia. Voice over IP (Wikipedia) last checked 2026-10
- Wikipedia. English Wikipedia article for Cisco Unified Border Element. confirm. That title returned HTTP 404. last checked 2026-10
- RFC. RFC 3261, SIP last checked 2026-10
- RFC. RFC 3550, RTP last checked 2026-10
- RFC. RFC 3711, SRTP last checked 2026-10
- Protocol and ports. CUCM 15 TCP and UDP port usage last checked 2026-10
- RFC. RFC 4566, SDP last checked 2026-10
- Cisco. Cisco Unified SRST product support last checked 2026-10
- Cisco. Cisco Unified Communications Manager product support last checked 2026-10
- Cisco. System Configuration Guide for CUCM, Release 15 last checked 2026-10
- Wikipedia. English Wikipedia article for Survivable Remote Site Telephony. confirm. That title returned HTTP 404. last checked 2026-10
- Webex. Get started with Local Gateway last checked 2026-10
- Webex. Configure Local Gateway on Cisco IOS XE for Webex Calling last checked 2026-10
- Webex. Get started with Webex Calling last checked 2026-10
- Protocol and ports. Port reference for Webex Calling last checked 2026-10
Dial peers
A dial peer matches an incoming or outgoing call.
CUBE as a B2BUA
CUBE terminates one dialog and starts another.
SRST
SRST is the fallback when phones cannot reach CUCM.
Local gateway toward Webex Calling
The local gateway is how premises PSTN or a PBX meets Webex Calling.
Sources and go deeper
Opened 2026-10. A row marked confirm has no link, because that page was not verified.
- Cisco. Understand IOS and IOS XE call routing last checked 2026-10
- Cisco. CUBE configuration guide, dial peers (IOS XE 17.6 onwards) last checked 2026-10
- RFC. RFC 4733, RTP telephony events last checked 2026-10
- Cisco. Cisco Unified Border Element product support last checked 2026-10
- Protocol and ports. IANA SIP parameters last checked 2026-10
- Protocol and ports. IANA service names and port numbers last checked 2026-10
- Community. Cisco Community, Collaboration knowledge base last checked 2026-10
- Wikipedia. Session Initiation Protocol (Wikipedia) last checked 2026-10
- Wikipedia. Voice over IP (Wikipedia) last checked 2026-10
- Wikipedia. English Wikipedia article for Cisco Unified Border Element. confirm. That title returned HTTP 404. last checked 2026-10
- RFC. RFC 3261, SIP last checked 2026-10
- RFC. RFC 3550, RTP last checked 2026-10
- RFC. RFC 3711, SRTP last checked 2026-10
- Protocol and ports. CUCM 15 TCP and UDP port usage last checked 2026-10
- RFC. RFC 4566, SDP last checked 2026-10
- Cisco. Cisco Unified SRST product support last checked 2026-10
- Cisco. Cisco Unified Communications Manager product support last checked 2026-10
- Cisco. System Configuration Guide for CUCM, Release 15 last checked 2026-10
- Wikipedia. English Wikipedia article for Survivable Remote Site Telephony. confirm. That title returned HTTP 404. last checked 2026-10
- Webex. Get started with Local Gateway last checked 2026-10
- Webex. Configure Local Gateway on Cisco IOS XE for Webex Calling last checked 2026-10
- Webex. Get started with Webex Calling last checked 2026-10
- Protocol and ports. Port reference for Webex Calling last checked 2026-10