Network+ (N10-009) · ELI Explains Port Numbers (book)
Ports Certification Exams Expect You to Know
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Certification objectives differ and no exam publishes one universal port list. This table collects common foundational associations from the detailed entries in this book. Learn what each service does rather than memorizing a number without context.
The college version
| Port | Why It Matters |
|---|---|
| 20 | FTP data in active mode |
| 21 | FTP control and commands |
| 22 | SSH and SFTP |
| 23 | Telnet; insecure remote terminal |
| 25 | SMTP server-to-server relay |
| 53 | DNS over UDP and TCP |
| 67 | DHCP server |
| 68 | DHCP client |
| 69 | TFTP |
| 80 | HTTP |
| 88 | Kerberos authentication |
| 110 | POP3 |
| 123 | NTP |
| 143 | IMAP |
| 161 | SNMP queries |
| 162 | SNMP traps |
| 389 | LDAP; may use StartTLS |
| 443 | HTTPS and HTTP/3 |
| 445 | SMB |
| 465 | Message submission over implicit TLS |
| 587 | Message submission, commonly with STARTTLS |
| 636 | LDAP over implicit TLS |
| 993 | IMAP over implicit TLS |
| 995 | POP3 over implicit TLS |
| 3389 | RDP |
Study tip: cover the right column and explain the service, transport behavior, and secure alternative in your own words.
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