| TCP Port | TCP/UDP | Service |
| 20 | TCP | FTP data port |
| 21 | TCP | FTP control port |
| 22 | TCP | SSH, SCP, SFTP |
| 23 | TCP | Telnet |
| 25 | TCP | SMTP |
| 49 | TCP/UDP | TACACS, TACACS+ |
| 53 | TCP/UDP | DNS |
| 67 | UDP | BOOTP server, also DHCP |
| 68 | UDP | BOOTP client, also DHCP |
| 69 | UDP | TFTP |
| 80 | TCP/UDP | HTTP |
| 88 | TCP/UDP | Kerberos authentication system |
| 118 | TCP/UDP | SQL |
| 123 | UDP | NTP |
| 143 | TCP | IMAP |
| 156 | TCP/UDP | SQL |
| 161 | UDP | SNMP |
| 162 | TCP/UDP | SNMP/TRAP |
| 179 | TCP | BGP |
| 220 | TCP/UDP | IMAP v3 |
| 389 | TCP | LDAP |
| 443 | TCP/UDP | HTTPS uses TCP in v 1.x and 2 HTTP/3 uses QUIC on top of UDP |
| 445 | TCP/UDP | Microsoft-DS – Active Directory, SMB |
| 464 | TCP/UDP | Kerberos change/set password |
| 500 | UDP | ISAKMP / IKE |
| 514 | UDP | Syslog |
| 543 | TCP | Kerberos login |
| 544 | TCP | Kerberos remote shell |
| 546 | TCP/UDP | DHCPv6 client |
| 547 | TCP/UDP | DHCPv6 server |
| 554 | TCP/UDP | RTSP |
| 601 | TCP | Reliable syslog service |
| 636 | TCP | LDAP over TLS/SSL (LDAPS) |
| 639 | TCP/UDP | MSDP (multicast) |
| 646 | TCP/UDP | LDP (MPLS) |
| 647 | TCP | DHCP failover |
| 694 | TCP/UDP | Linux HA heartbeat |
| 701 | TCP | LMP (TE) |
| 749 | TCP/UDP | Kerberos admin |
| 750 | UDP | Kerberos version IV |
| 830 | TCP/UDP | NETCONF over SSH |
| 831 | TCP/UDP | NETCONF over BEEP |
| 832 | TCP/UDP | NETCONF for SOAP over HTTPS |
| 833 | TCP/UDP | NETCONF for SOAP over BEEP |
| 847 | TCP/UDP | DHCP failover |
| 853 | TCP | DNS over TLS |
| 853 | UDP | DNS over QUIC or DNS over DTLS |
| 873 | TCP | rsync |
| 953 | TCP | BIND |
| 989 | TCP/UDP | FTPS (control), FTP over TLS/SSL |
| 990 | TCP/UDP | FTPS (data), FTP over TLS/SSL |
| 1812 | TCP/UDP | RADIUS authentication |
| 1813 | TCP/UDP | RADIUS accounting |
| 4500 | UDP | IPSEC NAT-T |
| 49152 – 65535 | TCP/UDP | Dynamic ports |