350-801 Question #440: Real Exam Question with Answer & Explanation

Question

An administrator troubleshoots a DNS issue with Cisco UCM and observes that the hostname resolution returns the wrong IP address. The DNS team informs the administrator that the A/AAA record was recently updated on the DNS server. Which action must be taken on Cisco UCM to reflect the correct entries?

Options

• ARestart the DNS server to flush any stale entries
• BFlush the current cache using this CLI command: admin:utils network name-service hosts cache
• CDelete the arp entry of the host utils network arp delete
• DFlush the current cache using this CLI command: admin:utils network name-service hosts cache

Explanation

When DNS records are updated but Cisco UCM still resolves to stale IP addresses, the CUCM's internal DNS cache needs to be cleared. The admin:utils network name-service hosts cache CLI command is used to flush this cache.

Common mistakes.

• A. Restarting the DNS server is outside the scope of UCM administration and would affect all clients using that DNS server; the issue is with UCM's local cache.
• C. Deleting the ARP entry using utils network arp delete would clear the MAC-to-IP mapping, which is unrelated to hostname-to-IP resolution issues.
• D. This option is identical to B, making B the correct answer as it is the appropriate CLI command to flush the DNS cache on Cisco UCM.

Concept tested. Cisco UCM DNS cache management

Reference. https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/cli_reference/8_0_2/cli_reference_802/cli_network.html

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