Network Ports and Protocols and What They’re Used For

Published October 20, 2023

Reviewed by Jeff Kish, CCIE


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

Port Number

Service Name

Description

Protocol

Ports 20-21

FTP

File Transfer Protocol

TCP

Port 22

SSH

Secure Shell; used for secure logins, file transfers, and port forwarding

TCP

Port 23

Telnet

Telnet protocol; used for unencrypted text communications

TCP / UDP

Port 25

SMTP

Simple Mail Transfer Protocol, used for email routing between mail servers

TCP

Port 53

DNS

Domain Name System; translates 'host names' into IP addresses

TCP / UDP

Port 69

TFTP

Trivial File Transfer Protocol

UDP

Port 80

HTTP

Hypertext Transfer Protocol; used for unencrypted web traffic

TCP

Port 102

ISO-TSAP

ISO Transport Service Access Point (TSAP)

TCP / UDP

Port 110

POP3

Post Office Protocol; used to connect to a mail server to retrieve emails

TCP / UDP

Port 123

NTP

Network Time Protocol

UDP

Port 135

DCE/RPC Endpoint Mapper

Distributed Computing Environment / Remote Procedure Call (DCE/RPC) Endpoint Mapper

TCP / UDP

Port 139

NetBIOS-ssn

NetBIOS Session Service

TCP / UDP

Port 161

SNMP-agents

Simple Network Management Protocol; agents communicate on this port

TCP / UDP

Ports 381 - 383

HP Performance Data Collector

Collects performance data from managed nodes

TCP / UDP

Port 389

LDAP

Lightweight Directory Access Protocol

TCP / UDP

Port 443

HTTPS

Hypertext Transfer Protocol Secure; used for encrypted web traffic

TCP / UDP

Port 445

Microsoft DS SMB

Microsoft Directory Services; TCP used for AD and Windows shares, UDP for SMB file-sharing

TCP / UDP

Port 464

Kerberos

Used for changing or setting passwords in Kerberos-based authentication systems, such as Active Directory

TCP / UDP

Port 465

SMTP

Simple Mail Transfer Protocol; used to securely transmit mail messages from email clients to email servers.

TCP

Port 514

syslog

Syslog Protocol; for collecting and organizing all log files sent from various devices on a network

UDP

Port 587

SMTP

Simple Mail Transfer Protocol; used for email message submission

UDP

Port 593

HTTP

Used for HTTP RPC EPMAP, which enables RPC clients to discover RPC servers, supporting efficient communication

TCP / UDP

Port 636

LDAP / LDAPS

Lightweight Directory Access Protocol (over SSL); used to store data in the LDAP directory and authenticate users to access the directory

TCP / UDP

Port 691

OSPF

Used by Microsoft Exchange Routing

TCP

Port 902

VMware vSphere

Used to manage your ESXi hosts and the virtual machines (VMs) that run on them

TCP / UDP

Port 993

IMAP

Internet Message Access Protocol; used to deliver and manage messages on email servers on behalf of email clients

TCP

Port 995

POP3

Post Office Protocol version 3 (over SSL); lets email users download messages from an email server using an email client

TCP / UDP

Port 1433

Microsoft SQL Server

Allows encrypted access to and management of databases and servers

TCP

Port 1521

Oracle Database

Oracle client apps communicate with Oracle database servers

TCP

Port 3306

MySQL

Used to connect with MySQL clients and utilities

TCP

Port 3389

Remote Desktop Protocol

Allows client device to remotely access and control a Windows desktop computer over this port

TCP

Port 5060

SIP

Session Initiation Protocol; used to signal and control communication sessions

TCP / UDP

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/Systems 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?

After Well Known ports is the next range of port numbers, which 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 fall between 49152 and 65535. Unlike Well Known or Registered port numbers, these ports can be used without any restriction.

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