Start with the must-know set
Filter to the must-know ports first. They show up on A+, Network+ and Security+, and in real troubleshooting every week.
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Common Ports Cheat Sheet
The well-known ports IT exams expect you to know, with TCP or UDP, what each is for and the secure protocol to use instead. Search them, then quiz yourself both ways.
Last updated
48 ports
20, 21
TCP
FTPMust know
File transfer
File Transfer Protocol
Transfers files; 21 carries commands, 20 carries data in active mode. Sends credentials in cleartext.
Use instead: SFTP (22) or FTPS (989, 990)
22
TCP
SSHMust know
Remote access
Secure Shell
Encrypted remote command line; SFTP and SCP file transfers run over it too.
23
TCP
TelnetMust know
Remote access
Telnet
Unencrypted remote terminal, still found on old network gear.
Use instead: SSH (22)
25
TCP
SMTPMust know
Email
Simple Mail Transfer Protocol
Relays email between mail servers.
Use instead: SMTP with STARTTLS, or SMTPS (465)
49
TCP
TACACS+
Directory and authentication
Terminal Access Controller Access-Control System Plus
Cisco’s AAA protocol for administrator logins to network devices; encrypts the whole payload.
53
TCP and UDP
DNSMust know
Network services
Domain Name System
Resolves names to IP addresses: UDP for most queries, TCP for zone transfers and large responses.
Use instead: DNS over TLS (853) or DNS over HTTPS (443)
67, 68
UDP
DHCPMust know
Network services
Dynamic Host Configuration Protocol
Hands out IP addresses and settings; servers listen on 67, clients on 68.
69
UDP
TFTPMust know
File transfer
Trivial File Transfer Protocol
Simple file transfer with no login, used for device configs and PXE boot.
Use instead: SFTP (22)
80
TCP
HTTPMust know
Web
Hypertext Transfer Protocol
Unencrypted web traffic.
Use instead: HTTPS (443)
88
TCP and UDP
Kerberos
Directory and authentication
Kerberos
Ticket-based authentication, the default in Active Directory domains.
110
TCP
POP3Must know
Email
Post Office Protocol v3
Downloads email from a server to one device, usually removing it from the server.
Use instead: POP3S (995)
123
UDP
NTPMust know
Network services
Network Time Protocol
Synchronizes clocks, which logs, certificates and Kerberos depend on.
135
TCP
RPC
File and print sharing
Microsoft RPC endpoint mapper
Locates Windows RPC services such as DCOM and WMI.
137–139
TCP and UDP
NetBIOSMust know
File and print sharing
NetBIOS over TCP/IP
Legacy Windows name service (137 UDP), datagrams (138 UDP) and sessions (139 TCP).
143
TCP
IMAPMust know
Email
Internet Message Access Protocol
Reads email that stays on the server, synced across devices.
Use instead: IMAPS (993)
161, 162
UDP
SNMPMust know
Management and logging
Simple Network Management Protocol
Monitors and manages devices: 161 for queries to agents, 162 for traps they send.
Use instead: SNMPv3 (authentication and encryption)
179
TCP
BGP
Routing
Border Gateway Protocol
Exchanges routes between networks on the internet.
389
TCP and UDP
LDAPMust know
Directory and authentication
Lightweight Directory Access Protocol
Queries and updates directories such as Active Directory.
Use instead: LDAPS (636)
443
TCP
HTTPSMust know
Web
HTTP over TLS
Encrypted web traffic; HTTP/3 also uses UDP 443.
445
TCP
SMBMust know
File and print sharing
Server Message Block
Windows file and printer sharing directly over TCP.
465
TCP
SMTPS
Email
SMTP over TLS
Email submission with TLS from the first byte.
500
UDP
IKE
VPN
Internet Key Exchange (ISAKMP)
Negotiates the keys for IPsec VPN tunnels.
514
UDP
SyslogMust know
Management and logging
Syslog
Sends log messages to a central collector or SIEM.
Use instead: Syslog over TLS (6514)
520
UDP
RIP
Routing
Routing Information Protocol
Distance-vector routing between routers.
587
TCP
SMTP submissionMust know
Email
Mail submission with STARTTLS
Where email clients send outgoing mail, upgraded to TLS with STARTTLS.
631
TCP
IPP
File and print sharing
Internet Printing Protocol
Network printing, used by CUPS and modern printers.
636
TCP
LDAPSMust know
Directory and authentication
LDAP over TLS
Encrypted directory queries.
853
TCP
DoT
Network services
DNS over TLS
Encrypted DNS lookups.
989, 990
TCP
FTPS
File transfer
FTP over TLS
FTP with TLS encryption: 990 for control, 989 for data.
993
TCP
IMAPSMust know
Email
IMAP over TLS
Encrypted IMAP email access.
995
TCP
POP3SMust know
Email
POP3 over TLS
Encrypted POP3 email download.
1194
UDP
OpenVPN
VPN
OpenVPN
OpenVPN’s default port (it can also run over TCP).
1433
TCP
MS SQLMust know
Databases
Microsoft SQL Server
Connections to Microsoft SQL Server databases.
1521
TCP
Oracle
Databases
Oracle Database listener
Connections to Oracle databases.
1701
UDP
L2TP
VPN
Layer 2 Tunneling Protocol
VPN tunnels, usually paired with IPsec for encryption.
1723
TCP
PPTP
VPN
Point-to-Point Tunneling Protocol
Legacy VPN with weak encryption; avoid it.
Use instead: IPsec, OpenVPN or WireGuard
1812, 1813
UDP
RADIUS
Directory and authentication
Remote Authentication Dial-In User Service
AAA for Wi-Fi (802.1X), VPN and network logins: 1812 authentication, 1813 accounting.
2049
TCP and UDP
NFS
File and print sharing
Network File System
File sharing between Linux and Unix systems.
3306
TCP
MySQLMust know
Databases
MySQL and MariaDB
Connections to MySQL and MariaDB databases.
3389
TCP and UDP
RDPMust know
Remote access
Remote Desktop Protocol
Graphical remote desktop to Windows machines.
4500
UDP
IPsec NAT-T
VPN
IPsec NAT traversal
Carries IPsec through NAT devices.
5060, 5061
TCP and UDP
SIPMust know
Voice
Session Initiation Protocol
Sets up VoIP calls: 5060 unencrypted, 5061 over TLS.
5432
TCP
PostgreSQL
Databases
PostgreSQL
Connections to PostgreSQL databases.
5900
TCP
VNC
Remote access
Virtual Network Computing
Cross-platform remote desktop.
5985, 5986
TCP
WinRM
Remote access
Windows Remote Management
PowerShell remoting: 5985 HTTP, 5986 HTTPS.
6514
TCP
Syslog over TLS
Management and logging
Syslog over TLS
Encrypted log forwarding.
8080
TCP
HTTP alternate
Web
HTTP alternate
Common port for web proxies and test web servers.
9100
TCP
Raw printing
File and print sharing
Raw printing (JetDirect)
Sends print jobs straight to a network printer.
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Guide
How to learn ports for good
Learn them in pairs
Most cleartext protocols have a secure twin: HTTP 80 and HTTPS 443, LDAP 389 and LDAPS 636, IMAP 143 and IMAPS 993, POP3 110 and POP3S 995, Telnet 23 and SSH 22.
Security+ often asks which port to allow or block after moving to the secure version.
Know TCP from UDP
Exams ask about the transport too. DHCP, TFTP, SNMP, NTP and Syslog use UDP; DNS uses both (UDP for queries, TCP for zone transfers).
Quiz both directions
Being able to go from port to service and from service to port is what makes them stick. Use “Quiz me” until you can answer the must-know set without a miss.
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FAQs
Got Questions? We’ve Got Answers.
Find quick answers or contact our support team.
Which ports are on CompTIA A+?
Expect FTP 20/21, SSH 22, Telnet 23, SMTP 25, DNS 53, DHCP 67/68, HTTP 80, POP3 110, NetBIOS 137–139, IMAP 143, SNMP 161/162, LDAP 389, HTTPS 443, SMB 445 and RDP 3389. Always check the current exam objectives for your version.
Which port is SFTP?
SFTP runs over SSH on TCP 22. FTPS, a different protocol, is FTP with TLS on 989 and 990.
Is DNS TCP or UDP?
Both. Ordinary lookups use UDP 53; zone transfers and responses too large for UDP use TCP 53.
What’s the difference between ports 465 and 587?
Both submit email securely. 465 uses TLS from the first byte (implicit TLS); 587 starts in plain text and upgrades with STARTTLS.
