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ExamsSY0-301Questions#816
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SY0-301 · Question #816

SY0-301 Question #816: Real Exam Question with Answer & Explanation

The correct answer is C: DNS. DNS (Domain Name System) operates on port 53 and is responsible for resolving human-readable domain names (e.g., www.example.com) into IP addresses. When users can reach websites by IP but not by name, it indicates that DNS resolution is failing - the firewall has blocked port 53

Question

A technician has just installed a new firewall onto the network. Users are reporting that they cannot reach any website. Upon further investigation, the technician determines that websites can be reached by entering their IP addresses. Which of the following ports may have been closed to cause this issue?

Options

  • AHTTP
  • BDHCP
  • CDNS
  • DNetBIOS

Explanation

DNS (Domain Name System) operates on port 53 and is responsible for resolving human-readable domain names (e.g., www.example.com) into IP addresses. When users can reach websites by IP but not by name, it indicates that DNS resolution is failing - the firewall has blocked port 53, preventing name lookups. HTTP (port 80) being blocked would prevent access even by IP. DHCP (port 67/68) handles IP address assignment; blocking it would prevent devices from getting an IP altogether. NetBIOS (port 137–139) is used for Windows file/printer sharing, not web browsing.

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