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 |
|---|---|---|---|
FTP | File Transfer Protocol | TCP | |
SSH | Secure Shell; used for secure logins, file transfers, and port forwarding | TCP | |
Telnet | Telnet protocol; used for unencrypted text communications | TCP / UDP | |
SMTP | Simple Mail Transfer Protocol, used for email routing between mail servers | TCP | |
DNS | Domain Name System; translates 'host names' into IP addresses | TCP / UDP | |
TFTP | Trivial File Transfer Protocol | UDP | |
HTTP | Hypertext Transfer Protocol; used for unencrypted web traffic | TCP | |
Kerberos | Used for secure network authentication, especially in Active Directory environments | TCP / UDP | |
ISO-TSAP | ISO Transport Service Access Point (TSAP) | TCP / UDP | |
POP3 | Post Office Protocol; used to connect to a mail server to retrieve emails | TCP / UDP | |
rpcbind | Portmapper service used to map RPC program numbers to network port numbers, typically used in NFS and other RPC services. | TCP / UDP | |
NTP | Network Time Protocol | UDP | |
DCE/RPC Endpoint Mapper | Distributed Computing Environment / Remote Procedure Call (DCE/RPC) Endpoint Mapper | TCP / UDP | |
NetBIOS-ssn | NetBIOS Session Service | TCP / UDP | |
SNMP-agents | Simple Network Management Protocol; agents communicate on this port | TCP / UDP | |
HP Performance Data Collector | Collects performance data from managed nodes | TCP / UDP | |
LDAP | Lightweight Directory Access Protocol | TCP / UDP | |
HTTPS | Hypertext Transfer Protocol Secure; used for encrypted web traffic | TCP / UDP | |
Microsoft DS SMB | Microsoft Directory Services; TCP used for AD and Windows shares, UDP for SMB file-sharing | TCP / UDP | |
Kerberos | Used for changing or setting passwords in Kerberos-based authentication systems, such as Active Directory | TCP / UDP | |
SMTP | Simple Mail Transfer Protocol; used to securely transmit mail messages from email clients to email servers. | TCP | |
syslog | Syslog Protocol; for collecting and organizing all log files sent from various devices on a network | UDP | |
SMTP | Simple Mail Transfer Protocol; used for email message submission | UDP | |
RPC Mapper Service | Enables secure remote connections and function execution over HTTP. | TCP / UDP | |
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 | |
Microsoft Exchange Routing Engine (RESvc) | Used by Microsoft Exchange servers to update routing tables for efficient message delivery. | TCP | |
VMware vSphere | Used to manage your ESXi hosts and the virtual machines (VMs) that run on them | TCP / UDP | |
IMAP | Internet Message Access Protocol; used to deliver and manage messages on email servers on behalf of email clients | TCP | |
POP3 | Post Office Protocol version 3 (over SSL); lets email users download messages from an email server using an email client | TCP / UDP | |
OpenVPN | Used by OpenVPN for establishing encrypted tunnels between VPN clients and servers | TCP / UDP | |
Microsoft SQL Server | Allows encrypted access to and management of databases and servers | TCP | |
Oracle Database | Oracle client apps communicate with Oracle database servers | TCP | |
MySQL | Used to connect with MySQL clients and utilities | TCP | |
Remote Desktop Protocol | Allows client device to remotely access and control a Windows desktop computer over this port | TCP | |
SIP | Session Initiation Protocol; used to signal and control communication sessions | TCP / UDP | |
mDNS | Multicast DNS (mDNS) is used for resolving hostnames to IP addresses within small networks without a local DNS server. | UDP | |
PostgreSQL | Used for communication between PostgreSQL clients and the database server | TCP | |
VNC (Virtual Network Computing) | Used for remote desktop sharing, allows a client to remotely view and control another computer's desktop | TCP | |
IRC (Internet Relay Chat) | Used for Internet Relay Chat (IRC) communications, enabling text-based communication over networks | TCP / UDP | |
BitTorrent | Used for peer-to-peer file sharing, facilitating data distribution across networks | TCP / UDP | |
Webmin | Used for remote server communication and configuration | TCP | |
NetBus | Used for remote administration; can be exploited for unauthorized access | TCP / UDP | |
Back Orifice / ncat | Used for remote control of servers by hacking tools and remote administration utilities | 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/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.