(ISC)2 Certified in Cybersecurity Practice Exam

What port range is known as the "well-known" ports?

1. 0 - 1,023

2. 0 - 1,000

3. 0 - 10,000

4. 0 - 65,535

The correct answer is: 0 - 1,023

The port range defined as "well-known" ports is from 0 to 1,023. This range is used by many popular protocols and services, including HTTP (port 80), FTP (port 21), and SMTP (port 25). These ports are established and assigned by the Internet Assigned Numbers Authority (IANA) for standard services and are recognized across all systems for network communications. Ports in this range are reserved for system or administrative purposes and require elevated privileges for applications to bind to them. This standardization is essential for ensuring consistent operation across various platforms and services, as it enables applications to reliably connect using commonly recognized ports. The other ranges mentioned, such as 0-1,000 or 0-10,000, extend beyond the defined well-known range, while the range 0-65,535 encompasses all possible ports, including both well-known ports and registered or dynamic ports. Thus, the correct identification of the well-known port range is crucial for understanding networking and cybersecurity fundamentals.