A+ network ports: choosing the service a scenario needs
Start with what the user needs: remote shell, file sharing, name resolution, email, or web access. Then identify the protocol and its conventional transport and port. Port numbers identify default service arrangements, not proof of what a captured application really is. DNS can use both TCP and UDP, and HTTPS does not imply that every connection uses the same transport.
How to read the scenario
Distinguish mail relay from client submission, and distinguish implicit TLS from an upgrade of an existing connection.
Identify the required outcome, the evidence already provided, and the limits on the technician’s action. Compare every option against those details before deciding. Record why the closest alternative does not meet the stated need.
Original practice example
A technician must permit a conventional DNS service through a firewall for both ordinary queries and operations that require reliable transport. Which TWO transport protocols can DNS use on port 53? Select TWO.
- ARP
- TCP
- UDP
- ICMP
Show the answer and explanation
TCP; UDP
DNS uses UDP and TCP on port 53. ICMP and ARP do not provide the DNS transport service.
Study questions
Which objective does this guide support?
220-1201, objective 2.1. This independent guide supports original practice and does not replace the full official objectives.
What should I watch for in a scenario?
Distinguish mail relay from client submission, and distinguish implicit TLS from an upgrade of an existing connection.
Source and version
CompTIA official 220-1201 objectives, objective 2.1. Verified November 5, 2026. Use the exam code when choosing study materials; similarly named certifications can have different objectives.