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Zorluk: OrtaNetworking Ports and Protocols

A desktop technician is troubleshooting a network connectivity issue on a user's workstation. The client computer can successfully ping external IP addresses (such as 8.8.8.8), but web browsers fail to load websites when navigating to URL domain names like www.comptia.org. Inspection of the local host firewall logs indicates that outbound traffic targeting an essential infrastructure service is being dropped. Which port and protocol combination must be permitted through the firewall to resolve this hostname resolution issue?

  1. UDP port 53Cevap
  2. B
    UDP port 67
  3. C
    TCP port 80
  4. D
    UDP port 123

Cevap

UDP port 53 must be allowed through the firewall because the Domain Name System (DNS) protocol handles name-to-IP address resolution over UDP port 53.
The ability to reach external network hosts by IP address combined with the inability to load sites by domain name indicates a Domain Name System (DNS) failure. DNS operates primarily on UDP port 53 to listen for and respond to hostname resolution requests from client systems.

Adım Adım Çözüm

1
Analyze the reported failure symptoms.
Pinging numerical IP addresses succeeds, confirming Layer 3 network connectivity, but navigating by domain names fails.
This specific failure pattern indicates that network routing is functional but name resolution services are failing.
2
Identify the protocol responsible for resolving hostnames to IP addresses.
Domain Name System (DNS) translates human-readable domain names into IP addresses.
Computers rely on DNS to query name servers when connecting via URLs.
3
Determine the default port and transport protocol for DNS queries.
DNS operates on port 53 using UDP for standard client queries (and TCP for zone transfers).
Permitting UDP port 53 on the host firewall allows DNS lookup requests and responses to pass through.

Anahtar Kavram

Domain Name System (DNS) Port and Transport Layer Protocol
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Konular

Networking Ports and Protocols

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