Troubleshooting

Sources and go deeper

Opened 2026-10. A row marked confirm has no link, because that page was not verified.

• Cisco. System Configuration Guide for CUCM, Release 15 last checked 2026-10
• RFC. RFC 3261, SIP last checked 2026-10
• Community. Cisco Community, Collaboration knowledge base last checked 2026-10
• Wikipedia. Session Initiation Protocol (Wikipedia) last checked 2026-10
• Protocol and ports. CUCM 15 TCP and UDP port usage last checked 2026-10
• RFC. RFC 3515, SIP REFER last checked 2026-10
• RFC. RFC 3264, offer/answer last checked 2026-10
• RFC. RFC 3550, RTP last checked 2026-10
• Cisco. Cisco Unified Border Element product support last checked 2026-10
• Cisco. Understand IOS and IOS XE call routing last checked 2026-10
• RFC. RFC 3711, SRTP last checked 2026-10
• RFC. RFC 8445, ICE last checked 2026-10
• Protocol and ports. Cisco Expressway IP port usage (X14.3 and X15.0) last checked 2026-10
• Wikipedia. Real-time Transport Protocol (Wikipedia) last checked 2026-10

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