# Mobile and Remote Access

- MRA lets a remote Cisco phone or Jabber register to CUCM through the Expressway pair.
- DNS SRV records point the client at Expressway-E.
- The registration still belongs to CUCM.
- Media traversal is a separate problem from the REGISTER.
- A VPN is a different design. Do not mix the words.

Users say the phone is 'on the VPN' when it is on MRA, or the reverse. The logs are different. MRA failures are often DNS, certificates, or the CUCM registration that never completes after the edge accepted the TLS session.

A remote phone resolves the edge, completes TLS to Expressway-E, and never appears on CUCM. The traversal zone is up, but the CUCM domain or the registration allow list on Expressway does not include that device. Look at the Expressway registration status and then CUCM.

## Sources and go deeper

Independent, free, learning-only student project.

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

- Cisco. [Mobile and Remote Access through Cisco Expressway, X15.2](https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/expressway/config_guide/X15-2/mra/exwy_b_mra-deployment-guide-x152.html). last checked 2026-10
- Cisco. [Cisco Expressway Series product support](https://www.cisco.com/c/en/us/support/unified-communications/expressway-series/series.html). last checked 2026-10
- Protocol and ports. [Cisco Expressway IP port usage (X14.3 and X15.0)](https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/expressway/config_guide/X15-0/ip-port/exwy_b_cisco-expressway-ip-port-usage-configuration-guide-x15.html). last checked 2026-10
- Cisco. [System Configuration Guide for CUCM, Release 15](https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/15/systemConfig/cucm_b_system-configuration-guide-15.html). last checked 2026-10
- Protocol and ports. [IANA service names and port numbers](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml). last checked 2026-10
- Community. [Cisco Community, Collaboration knowledge base](https://community.cisco.com/t5/collaboration-knowledge-base/tkb-p/4691-docs-collaboration-voice-video). last checked 2026-10
- Wikipedia. [Voice over IP (Wikipedia)](https://en.wikipedia.org/wiki/Voice_over_IP). last checked 2026-10

Room or sheet file: ../../rooms/sources/mra/sources.json