Common TCP & UDP Ports and Protocols

Last updated June 26, 2025

Reviewed by Jeff Kish, CCIE

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With more than 65,000 port numbers in existence, a list of common networking ports is not only helpful, but necessary. Especially if you’re studying for a networking certification exam like the Network+ or the CCNA. Both of these exams will test your knowledge of common ports and their associated services.

As a component of the Transport Layer (Layer 4 in the OSI model), TCP and UDP ports are the virtual places where network connections begin and end. Port numbers allow network-connected devices to transmit data using transmission protocols. Without port numbers, network traffic would be indecipherable.

This list of common TCP and UDP ports is by no means exhaustive, but does include ports that network administrators will be expected to use in their day-to-day role.

List of Common Ports and Protocols

Understanding TCP and UDP Protocols: Frequently Asked Questions

Ports and their affiliated numbers are used to identify specific applications and services. Port numbers are what allow apps on an IP network to communicate with the source and destination IP address and the transport protocol.

What is a Port Number?

Networking protocols use port numbers that are based on the type of packet being sent and/or received. A network host typically runs many software packages/processes, so when it receives a packet it looks to the port number to identify which process should get it.

How Do Port Numbers Work?

All network-connected devices are affiliated with a port that’s been assigned a number. These port numbers are standardized, and each is reserved for certain protocols.

Port identification numbers are used to ensure the correct information is being sent and received. For example, one port is used to send the packet, while another port is used to receive the data.

All port numbers target a service or application and are reserved for certain protocols.

Where Do Ports Fall Into the OSI Model?

Ports are a concept of Layer 4 — the Transport Layer. Transport protocols such as TCP and UDP indicate the port that a packet should go to.

What Are Well-Known/Systems Ports?

Port numbers that fall into the category of well-known/system ports include numbers between 0 and 1023. IP protocols use them for TCP, UDP, Telnet, and FTP.

These port numbers are only used by network admins, default applications, operating systems, and services. Users do not have access to this range of ports.

What are Registered Port Numbers?

The next range of port numbers after well-known ports includes ports 1024 through 49151. This range of ports is known as “Registered ports” because they are registered with the IANA (Internet Assigned Numbers Authority).

Unlike well-known port numbers, registered port numbers are used by network users.

What Are Dynamic/Private Port Numbers?

The final range of port numbers falls between 49152 and 65535. Unlike well-known or registered port numbers, these ports can be used without any restriction.