Exam 300-820 topic 1 question 98 discussion

https://community.cisco.com/legacyfs/online/jabber-mra-call_flow-detailed.pdf

https://www.cisco.com/c/en/us/support/docs/unified-communications/expressway/118798-technote-cucm-00.html#toc-hId-681856141 - "If port 8443 is not reachable, this is possibly because a security device (Firewall) blocks the port or a misconfiguration of the Default Gateway (GW) or Static routes in the Exp-E." Possible answers are BC. _cisco-uds is not relevant to MRA rather _collab-edge.

The two reasons that could be causing the Expressway-E to be unreachable on port 8443 from the internet are: C. The firewall is blocking the port: If the firewall is blocking port 8443, then traffic from the Jabber clients attempting to connect to the Expressway-E over this port will not be able to reach it. In this case, the firewall would need to be reconfigured to allow traffic on this port. E. The SRV record for _cisco-uds is misconfigured: The _cisco-uds DNS SRV record is used by Jabber clients to locate the Unified Communications Manager (CUCM) and other services. If this record is misconfigured, the Jabber client may not be able to connect to the Expressway-E or other services. The administrator should verify that the SRV record is configured correctly in the public DNS zone for the domain and that it resolves to the correct IP address for the Expressway-E.

The _collab-edge SRV record should point to the Fully Qualified Domain Name (FQDN) of Expressway-E with port 8443. If the _collab-edge SRV is not created, or is not externally available, or if it is available, but port 8443 is not reachable, then the Jabber client fails to log in. https://www.cisco.com/c/en/us/support/docs/unified-communications/expressway/118798-technote-cucm-00.html

_collab-edge SRV is used to get to the Exp-E's and _cisco-uds SRV is used to get to CUCM from the Exp-C's. If _cisco-uds is misconfigured, the Jabber client won't be able to get to CUCM and register.