Exam 300-820 topic 1 question 163 discussion

The DNS server addresses specify the IP addresses of up to five domain name servers to be used for resolving domain names. In either of the following cases you must specify at least one default DNS server for address resolution: To use fully qualified domain names instead of IP addresses when specifying external addresses. For example, for LDAP and NTP servers, neighbor zones and peers. To use features such as URI dialing or ENUM dialing. https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/expressway/config_guide/X14-0/basic_config/exwy_b_cisco-expressway-e-and-expressway-c-basic-configuration-deployment-guide-x14-0/exwy_m_expressway-system-configuration.html?bookSearch=true#concept_3FAF63C7A2CB513E4D8B2AFE40446BE4

Proper DNS configuration on Expressway servers is critical for: Verifying the common name in server certificates (A) Routing calls based on SIP URI (B)

This is a tricky question. The real trick on this is what requires a FQDN. A. Expressway servers verify the common name attribute in server certificates. I am leaning away from this one. The common name doesnt necessarily have to line up with a FQDN. B. Expressway servers route calls based on SIP URI. This is a definite yes. URI dialing requires a DNS server to be configured. C. Admins avoid IP address configuration for neighbor zone peers. I am leaning towards this one. You can only configure an IP address or FQDN. If you go FQDN, you need a DNS configured D. Expressway servers use NTP peer authentication for secure time updates. You can configure an IP address or FQDN here. I am discounting this because you can configure an IP address. E. Admins download software updates from the Cisco website via WebUI. Software updates are not obtained via WebUI for expressways. I was under the assumption that WebUI is only for select routers.