Important port number system admin need to know!
20 – FTP Data (For transferring FTP data) 21 – FTP Control (For starting FTP connection) 22 – SSH(For secure remote administration which uses SSL to encrypt the transmission) 23 – Telnet (For insecure remote administration) 25 – SMTP(Mail Transfer Agent for e-mail server such as SEND mail) 53 – DNS(Special service which uses both TCP and UDP) 67 – Bootp 68 – DHCP 69 – TFTP(Trivial file transfer protocol uses udp protocol for connection less transmission of data) 80 – HTTP/WWW(apache) 88 – Kerberos 110 – POP3(Mail delivery Agent) 123 – NTP(Network time protocol used for time syncing uses UDP protocol) 137 – NetBIOS(nmbd) 139 – SMB-Samba(smbd) 143 – IMAP 161 – SNMP(For network monitoring) 389 – LDAP(For centralized administration) 443 – HTTPS(HTTP+SSL for secure web access) 514 – Syslogd(udp port) 636 – ldaps(both tcp and udp) 873 – rsync 989 – FTPS-data 990 – FTPS 993 – IMAPS 1194 – openVPN 1812 – RADIUS 995 – POP3s 2049 –...
