Security+ ports and protocols to memorize

Port numbers are pure recall, which makes them ideal flashcard material. This list sticks to long-established, well-known assignments. It is a study list, not a copy of CompTIA's objectives: the SY0-701 objectives name protocols and acronyms, and you should read them for exactly what is in scope, including the ports and protocols listed there.

Remote access and administration

• SSH: 22 (TCP), the encrypted replacement for Telnet
• Telnet: 23 (TCP), cleartext, which is why it is a classic wrong answer
• RDP: 3389 (TCP), Windows remote desktop

Web

• HTTP: 80 (TCP)
• HTTPS: 443 (TCP), HTTP over TLS

Email

• SMTP: 25 (TCP), server-to-server mail transfer
• SMTP submission: 587 (TCP), client to server; 465 is also used for SMTP over implicit TLS
• POP3: 110 (TCP); POP3 over TLS: 995
• IMAP: 143 (TCP); IMAP over TLS: 993

Name and address services

• DNS: 53 (UDP for most queries, TCP for zone transfers and large responses)
• DHCP: 67 and 68 (UDP), server and client
• NTP: 123 (UDP), time synchronization

File transfer and sharing

• FTP: 21 for control, 20 for active-mode data (TCP), cleartext
• TFTP: 69 (UDP)
• SMB: 445 (TCP), Windows file sharing

Directory, authentication and monitoring

• Kerberos: 88
• LDAP: 389; LDAP over TLS (LDAPS): 636
• RADIUS: 1812 and 1813 (UDP), authentication and accounting
• SNMP: 161 (queries) and 162 (traps), UDP
• Syslog: 514 (UDP)

How to make them stick

Learn them in pairs. Cleartext and its secure sibling belong together: Telnet 23 and SSH 22, HTTP 80 and HTTPS 443, LDAP 389 and LDAPS 636, IMAP 143 and IMAPS 993, POP3 110 and POP3S 995. A quiz that asks "which one is the encrypted one" tests exactly what security exams care about.

Quiz from both sides. Practice port to protocol and protocol to port. Real exam questions come in both directions, often wrapped in a scenario about a firewall rule or a scan result.

Space the reviews. Ports are the kind of fact that fades in a week without review. Spaced repetition schedules each one just before you would forget it.

Related

Ports sit alongside addressing in networking questions, so pair this list with the subnet and CIDR calculator. For the bigger picture, see the five SY0-701 domains and Security+ vs Network+ vs A+. An Encodr Security+ course is in the works; the coming-soon page has the exam facts, and you can browse all exam prep courses.