Common Ports

FTP - 20 & 21

SSH, SCP, SFTP - 22

Telnet - 23

SMTP - 25

TACACS - 49

DNS - 53

DHCP - 67 & 68

TFTP - 69

HTTP - 80

Kerberos - 88

POP3 - 110

NetBIOS - 137-139

IMAP4 - 143

SNMP - 161

LDAP - 389

SSL & HTTPS - 443

SMB - 445

LDAP with SSL - 636

FTPs - 989 & 990

Microsoft SQL Server - 1433

Layer 2 Tunneling Protocol (L2TP) - 1701

Point-to-Point Tunneling Protocol (PPTP) - 1723

RDP protocol and Terminal Services - 3389