Common Ports Cheat Sheet

It’s a pain trying to memorize port numbers and their corresponding service names and protocols. So, we created this concise cheat sheet of common network ports and their associated protocols and service names for you to use as a quick reference.

Feel free to print it out and hang it up or share a link to it with your colleagues and peers. Use it to speed up port identification or as a training resource for onboarding new network administrators or engineers.

Free Common Port Cheat Sheet

Click on the network port chart above to view the printable, searchable PDF version. Scroll down below for the port list tables.

This list is by no means exhaustive. It just lists the most frequently used ports. There are a total of 65,535 TCP/UDP ports. They are divided into 3 classes:

• Well Known Ports (1-1023) – Reserved ports registered with IANA for specific services.
• Registered Ports (1024-49151) – Also registered with IANA but not as commonly used.
• Dynamic/Private Ports (49152-65535) – Reserved by IANA for proprietary services or private use.

IANA (Internet Assigned Numbers Authority), in case you’re wondering, is the organization that oversees global IP address allocation and port classification.

Some common protocols that use these ports:

• TCP (Transmission Control Protocol)
• UDP (User Datagram Protocol) – Only one port needed for bidirectional traffic
• SCTP (Stream Control Transmission Protocol)
• DCCP (Datagram Congestion Control Protocol)

Common Well-known/System Ports in Computer Networking

Well-known network ports range from 0 to 1023. These ports are assigned by IANA and listed in RFC 1700. On most systems they can only be used by system (or root) processes or by programs executed by privileged users. Some well-known ports use TCP, some use UDP, and some can be configured to use either.

Well-known TCP ports are used by applications that rely on TCP as the transport protocol. Examples:

• FTP (File Transport Protocol) uses TCP ports 20 and 21
• Telnet uses TCP port 23

Well-known UDP ports are used by applications relying on UDP. Examples:

• TFTP (Trivial File Transport Protocol) uses UDP port 69
• SNMP uses UDP port 161 for messages and UDP port 162 for traps

Knowledge of these ports is helpful for network engineers looking for work as they are popular topics asked about in technical interviews.

Common Registered Network Ports

Registered network ports are ports in the range of 1024 to 49151 that have been officially registered with the Internet Assigned Numbers Authority (IANA) for specific services and applications.

Some key points about registered ports:

• They come after well-known ports (0-1023) and before dynamic/private ports (49152-65535).
• Anyone can register a port in this range with IANA for their application/service.
• Registration ensures the port number is standardized and should not be used by other services.
• Examples include port 3306 for MySQL, port 1521 for Oracle database, port 1723 for PPTP.
• Not as commonly used as well-known ports, but still important for avoiding conflicts.
• Provide an official way to allocate ports for proprietary applications and organizational services.
• The full list of registered ports is maintained by IANA and published on their website.
• Helpful for network administration to know what traffic these registered ports are associated with.

Common Dynamic/Private Network Ports

Dynamic/Private network ports refer to the range of ports from 49152 to 65535 that are not officially registered with IANA for any specific service or application and are available for private or temporary use.

They can be used by applications dynamically as needed, usually for establishing temporary connections. Often they are used by client-side applications that initiate connections to servers on well-known or registered ports.

A common example of dynamic network port use is Ephemeral Ports. These are short-lived transport layer ports used when an application on a client device makes an outgoing connection to a server. They allow a client application to use a random available port for its side of the connection which has multiple benefits from enabling multiple connections from the same client application to traversing firewalls as most firewalls are configured by default to allow connections from ephemeral ports to well-known ports.

The dynamic/private port range also provides ports for private or customized services within an organization since they are unregistered.

Top 35 Most Common Ports for Certification Exams and Interviews

Prepping for an exam or interviewing for a role in networking or a networking adjacent field? Prioritize memorizing the ports below.

In my experience, these are the ports most frequently used in certification exams and to quiz candidates in technical interviews.

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