350-801 CLCOR: Implementing and Operating Cisco Collaboration Core TechnologiesDemo

By Cisco · Question Mode

QuestionQ480

On-Premises Call Control

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Refer to the exhibit. An engineer runs the utils diagnose test CLI command on a Cisco UCM subscriber and gets an error message during the validate_network test. What are two possible causes of this error?

Choose two
  • A The DNS server is missing PTR records for the Cisco UCM servers.
  • B A failure is expected when the utils diagnose test command is run on a subscriber.
  • C The DNS server has multiple PTR records for the Cisco UCM servers.
  • D The DNS servers are unreachable from the Cisco UCM server.
  • E The firewall is blocking UDP port 53 traffic from Cisco UCM to the DNS servers.
Explanation

A reverse DNS lookup resolves an IP address to a hostname through PTR records. Cisco UCM requires each server IP to have a valid, unambiguous reverse mapping. A missing PTR record prevents the lookup, while multiple PTR records can yield an ambiguous or nonmatching hostname and cause the reverse-DNS validation to fail.

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