IT and cloud certifications · 30 cards · sources listed below

Network Ports Flashcards

This set covers the well-known ports and protocols that IT certification exams and help-desk work keep returning to. Port numbers and service names were checked against the IANA Service Name and Port Number Registry. It is a starter set and does not cover every registered port.

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Server rack, cloud, terminal window, padlock and network nodes

Free Network Ports flashcards: 30-card starter set

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File transfer, remote access and web (8)

FTP uses which ports?

TCP 21 for control commands and TCP 20 for data transfer (in active mode). FTP sends credentials in clear text.

SSH port

TCP 22. Encrypted remote shell, and also the transport for SFTP and SCP.

Telnet port and why it is avoided

TCP 23. Remote terminal that sends everything, including passwords, unencrypted. Use SSH instead.

TFTP port

UDP 69. Trivial File Transfer Protocol: simple, no authentication, often used for booting devices and device configuration files.

HTTP and HTTPS ports

HTTP is TCP 80. HTTPS (HTTP over TLS) is TCP 443.

What is port 8080 commonly used for?

HTTP-Alt: an alternate HTTP port, often used for proxies and development web servers.

RDP port

TCP 3389 (registered as MS WBT Server). Remote Desktop Protocol for Windows graphical remote access.

Which secure protocol replaces Telnet, and which replaces FTP?

SSH replaces Telnet. SFTP (over SSH, port 22) or FTPS (FTP over TLS) replaces FTP.

Email (5)

SMTP port

TCP 25 for server-to-server mail transfer.

Message submission ports (587 and 465)

Port 587 is the standard mail submission port for clients sending to their server. Port 465 is registered for message submission over TLS (submissions).

POP3 and POP3S ports

POP3 is TCP 110. POP3 over TLS is TCP 995.

IMAP and IMAPS ports

IMAP is TCP 143. IMAP over TLS is TCP 993.

POP3 vs IMAP

POP3 typically downloads mail to one device. IMAP keeps mail on the server and syncs folders and state across devices.

Addressing, naming and management (7)

DNS port

Port 53, over both UDP and TCP. UDP handles normal queries; TCP is used for large responses and zone transfers.

DHCP server and client ports

UDP 67 on the server and UDP 68 on the client (registered as BOOTP server and client).

NTP port

UDP 123. Network Time Protocol synchronizes clocks.

SNMP and SNMP trap ports

UDP 161 for polling and queries; UDP 162 for traps (unsolicited alerts from devices).

Syslog port

UDP 514. Used to send log messages to a central log server.

Kerberos port

Port 88 (TCP and UDP). Ticket-based authentication used in Windows Active Directory.

SIP ports

5060 for SIP and 5061 for SIP over TLS. Used to set up VoIP calls.

Directory, file sharing and databases (5)

LDAP and LDAPS ports

LDAP is port 389. LDAP over TLS (LDAPS) is port 636.

SMB over TCP port

TCP 445 (registered as Microsoft-DS). Windows file and printer sharing.

Microsoft SQL Server default port

TCP 1433.

MySQL default port

TCP 3306.

PostgreSQL default port

TCP/UDP 5432 (registered as PostgreSQL Database); used over TCP in practice.

Port concepts and TCP vs UDP (5)

The three port number ranges

System/well-known 0-1023, user/registered 1024-49151, and dynamic/private 49152-65535 (RFC 6335).

TCP vs UDP

TCP is connection-oriented and reliable, with ordering and retransmission. UDP is connectionless, with no delivery guarantee, but lower overhead and delay.

TCP three-way handshake

SYN, then SYN-ACK, then ACK.

Why do DNS queries usually use UDP?

One small request and one small reply are quicker without connection setup. TCP is used when responses are too large or for zone transfers.

Which would you use for live video calls: TCP or UDP?

Usually UDP. A slightly late packet is useless, so retransmission delay hurts more than a lost packet.

What this set covers

Ports covered

File transfer, remote access, email, DNS and DHCP, time and management, directory, Windows file sharing and common databases.

Best used for

Memorizing ports for networking and security certification exams, and for firewall and troubleshooting work.

Not covered

Every registered port, vendor-specific ports, and ephemeral port behavior beyond the basics.

Source of truth

IANA registry. Some applications can be configured to use other ports.

How to study this set

Port lists are pure recall, so short spaced reviews work better than one long memorization session.

1
Day 1
Learn only the groups for web, remote access and email. Say each protocol and port aloud as a pair.
2
Days 2-7
Add one group per day. Quiz both directions: protocol to port and port to protocol.
3
Week 2
Group by secure vs insecure pairs (23 vs 22, 110 vs 995, 389 vs 636) and recite them.
4
Final week
Write the full list from memory on paper, then check against the deck and review the misses.

Spaced repetition schedules each card to come back just before you would forget it, so reviews get shorter as your recall gets stronger. Cards you miss come back sooner.

Common mistakes to avoid

Learning only one direction

Exams give you the port and ask for the protocol as often as the reverse. Study both.

Mixing up the secure variants

Remember POP3 110 vs POP3S 995, IMAP 143 vs IMAPS 993, LDAP 389 vs LDAPS 636.

Forgetting UDP ports

DHCP, TFTP, NTP, SNMP and syslog are UDP-based; do not default everything to TCP.

Assuming the port proves the protocol

Software can run on non-default ports, and a port number does not guarantee what is actually running.

Make your own from your notes

A starter set is a head start, not your whole course. Your class notes, slides and textbook are what your teacher actually tests, so turn them into cards too.

Put the protocol name on the front and "port + TCP/UDP + one-line purpose" on the back.
Make a second set with the port on the front so you practice both directions.
Add a secure-alternative card for every insecure protocol.
Keep one port per card; do not put a whole table on a single card.

Generate cards from a topic or notes Turn a PDF into flashcards

Network Ports flashcards: questions

Where do these port numbers come from?

The numbers and service names were checked against the IANA Service Name and Port Number Registry, which assigns the well-known and registered ports.

Does FTP use port 20 or 21?

Both. Port 21 carries control commands and port 20 is registered for data, used in active mode. Passive mode uses a negotiated higher port for data.

Why does DNS use both UDP and TCP?

Typical queries are small and use UDP. TCP is used when a response is too large for a UDP reply and for zone transfers between servers.

Do I need to know all 65,535 ports?

No. Certification exams focus on a few dozen well-known ports. Start with the ones in this deck and add any your exam objectives list.

Sources and review

These cards are an independent study aid, not official exam content, and are not affiliated with or endorsed by any exam body or publisher. They were written by hand and checked against the sources below on 2026-10-17. Always confirm details with your course materials and the current official documents.

IANA Service Name and Port Number Registry — Port numbers, service names and transport protocols in every port card (checked from the registry CSV).
RFC 6335: IANA procedures for service names and ports — Port number ranges.

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