Well-Known ports

The port numbers in the range from 0 to 1023 (0 to 2^10 − 1) are the well-known ports or system ports. They are used by system processes that provide widely used types of network services.

This is a partial list of the Well-Known ports (WKP). This is the most common ports a Net Admin will have to manage on the public side of a Firewall (NAT/PAT).

Well-Known ports

Port	TCP	UDP	NAME	USE FOR	Description
20	✓		FTP – data	FILE	File Transfer Protocol data transfer
21	✓		FTP – command	FILE	File Transfer Protocol (control (command)
22	✓		SSH	REMOTE CONSOLE	Secure Shell, secure logins, file transfers (scp, sftp) and port forwarding
23	✓		TELNET	REMOTE CONSOLE	Telnet protocol—unencrypted text communications
25	✓		SMTP	EMAIL	Simple Mail Transfer Protocol, used for email routing between mail servers
53	✓	✓	DNS	NAME RESOLUTION	Domain Name System
67		✓	BOOTP/DHCP	IP ADDRESS	Bootstrap Protocol client; also used by Dynamic Host Configuration Protocol
68		✓	BOOTP/DHCP	IP ADDRESS	Bootstrap Protocol client; also used by Dynamic Host Configuration Protocol
69		✓	TFTP	FILE	Trivial File Transfer Protocol
80	✓	✓	HTTP	WEB	Hypertext Transfer Protocol uses TCP in versions 1.x and 2
110	✓		POP3	EMAIL	Post Office Protocol, version 3
123		✓	NTP	TIME SYNC	Network Time Protocol, used for time synchronization
137	✓	✓	NETBIOS	NAME RESOLUTION	NetBIOS Name Service, used for name registration and resolution
138		✓	NETBIOS	NAME RESOLUTION	NetBIOS Datagram Service
139	✓		NETBIOS	NAME RESOLUTION	NetBIOS Session Service
143	✓		IMAP	EMAIL	Internet Message Access Protocol, management of electronic mail messages on a server
161		✓	SNMP	MANAGEMENT	Simple Network Management Protocol
162	✓	✓	SNMPTRAP	MANAGEMENT	Simple Network Management Protocol Trap
220	✓	✓	IMAP	EMAIL	Internet Message Access Protocol, version 3
443	✓	✓	HTTPS	WEB	Hypertext Transfer Protocol Secure uses TCP in versions 1.x and 2
465	✓		SMTP/S	EMAIL	Authenticated SMTP over TLS/SSL
500		✓	ISAKMP/IKE	ENCRYPTION/VPN	Internet Security Association and Key Management Protocol / Internet Key Exchange
514		✓	SYSLOG	LOGGIN	Syslog, used for system logging
554	✓	✓	RTSP	STREAMING	Real Time Streaming Protocol
853	✓	✓	DNS/S	NAME RESOLUTION	DNS over TLS

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