Common TCP Ports for A+
Short answer
Technician-level support requires quick recognition: knowing that certain services normally listen on a known TCP port is essential for troubleshooting blocked connections, firewall rules, and service identification. For example, if users cannot access a secure site, HTTPS on 443 is the expected destination. If remote CLI access is needed securely, SSH on 22 is the expected service.
Why it appears on the exam
- Direct recognition: Given a service name, select the default TCP port (e.g., Which port for RDP?). - Scenario matching: Given a symptom (cannot reach secure site), choose the likely protocol and port. - Short justification: Explain why SSH is preferred over Telnet for remote management.
Key concepts
Concept 1
Required terms
FTP (20,21): File Transfer Protocol: legacy file transfer service; control on 21, data often on 20. Typically TCP. SSH (22): Secure Shell: encrypted remote command-line administration over TCP. Telnet (23): Insecure remote command-line protocol that transmits credentials in plain text; TCP-based. SMTP (25): Simple Mail Transfer Protocol: used to send email between servers; TCP-based.
Example
A user cannot access a secure admin web page -> check HTTPS (443) and web server reachability.
Concept 2
How Common TCP Ports works
Technician-level support requires quick recognition: knowing that certain services normally listen on a known TCP port is essential for troubleshooting blocked connections, firewall rules, and service identification. For example, if users cannot access a secure site, HTTPS on 443 is the expected destination. If remote CLI access is needed securely, SSH on 22 is the expected service.
Example
An admin reports inability to SSH into a server -> check port 22 and firewall rules.
Concept 3
Common confusion
- Mixing up SMTP (sending) with POP3/IMAP (retrieval). - Treating Telnet and SSH as interchangeable; Telnet is insecure. - Expecting older port assignments (NetBIOS 137-139) instead of modern direct SMB on 445.
Example
Shared network drives unavailable -> investigate SMB on port 445.
Concept 4
Core 1 (220-1201) question cues
Direct recognition: Given a service name, select the default TCP port (e.g., Which port for RDP?); Scenario matching: Given a symptom (cannot reach secure site), choose the likely protocol and port; Short justification: Explain why SSH is preferred over Telnet for remote management.
Example
A user cannot access a secure admin web page -> check HTTPS (443) and web server reachability.
Sample questions
Select an answer to reveal the explanation. For tracked practice and weak-area review, use the Cultiv8 app.
Q1.An A+ support scenario describes this situation: A user cannot access a secure admin web page -> check HTTPS (443) and web server reachability. Which answer fits best?
Q2.A support ticket includes this clue: An admin reports inability to SSH into a server -> check port 22 and firewall rules. Which concept is being tested?
Q3.Read this A+ scenario: Shared network drives unavailable -> investigate SMB on port 445. Which term or action matches it?
Practice this lesson in Cultiv8
The app adds tracked practice, targeted remediation, saved session history, and future readiness scoring.
Continue in Cultiv8