Ports help devices know where the traffic goes by scanning their packets’ port numbers assigned by the sender’s computer. It acts as a filter to prevent network packets from entering the wrong software.
For example, a Packet with port number 143 should only reach the email server, not the HTTP server for websites.
In IPv4, port numbers range from 0 to 65535, while Well-Known Ports range from 0 to 1023.
Firewalls use Port Numbers to block unnecessary traffic and reduce the risk of hackers breaking in and other cyber attacks.
To ace the CompTIA Core 1 Exam, you only need to remember these common “Well-Known Ports” and their service.
| 20/21 -FTP | 137/139 – NetBIOS |
| 22 – SSH | 143 – IMAP |
| 23 – Telnet | 161/162 – SNMP |
| 25 – SMTP | 389 – LDAP |
| 53 – DNS | 443 – HTTPS |
| 67/68 – DHCP | 445 – SMB |
| 80 – HTTP | 3389 – RDP |
| 110 – POP3 |