By default, on which port does the Squid proxy server listen for incoming client requests?

Introduction / Context:
Squid is a widely used proxy server for caching and filtering web traffic. One of the first steps in configuration or troubleshooting is knowing which TCP port it listens on by default.

Given Data / Assumptions:

• The service in question is Squid proxy server.
• No custom configuration has been applied yet.

Concept / Approach:

By default, Squid listens on port 3128. This port is chosen historically and is distinct from port 80 (HTTP) or 443 (HTTPS). Administrators can change this value in the configuration file (squid.conf) if required.

Step-by-Step Solution:

Verification / Alternative check:

Examine /etc/squid/squid.conf for http_port directive. Unless modified, it is set to 3128.

Why Other Options Are Wrong:

• 4322, 2314, 7334: arbitrary numbers, not Squid defaults.
• None of the above: incorrect because 3128 is correct.

Common Pitfalls:

• Confusing port 3128 with port 8080, which is sometimes used as an alternative proxy port.
• Assuming Squid listens on HTTP (80) by default—it does not.

Final Answer:

3128.