Question 1

What are well-known ports?

Accepted Answer

Well-known ports (0-1023) are assigned by IANA for standard services like HTTP (80), HTTPS (443), SSH (22), and FTP (21). They require elevated privileges to bind on most operating systems.

Question 2

What are registered ports?

Accepted Answer

Registered ports (1024-49151) are assigned by IANA for specific services or applications. Examples include MySQL (3306), Redis (6379), and PostgreSQL (5432).

Question 3

What are dynamic/ephemeral ports?

Accepted Answer

Dynamic ports (49152-65535) are used by client applications for temporary connections. They are not assigned to specific services.

Question 4

Which ports should I keep closed for security?

Accepted Answer

Close ports for services you don't use. Telnet (23), FTP (21), and RPC (135) should typically be closed. Use SSH (22) instead of Telnet, SFTP instead of FTP.

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