Common Services And Ports Used

DNS Domain Name System 53
POP3 Post Office Protocol 110
SMTP Simple Mail Transfer Protocol 25
SNMP Simple Network Management Protocol 160,161
NNTP Network News Transfer Protocol 119
FTP File Transfer Protocol 20,21
SSL Secure Sockets Layer 443
TELNET 23
TACACS authentication 49
HTTP 80
HTTPS 443
NetBIOS 137,138,139
IMAP 143
LDAP 389
LDAP SSL 636
SSH Secure Shell 22
AH, ESP ports 50 and 51
BOOTP server 67 UDP
BOOTP Client 68 UDP
TFTP 69 UDP
NTP 123
BGP 179
SYSLOG 514
MSSQL 1433
RDP 3389
VNC 5500