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What is rp_filter and what is it used for?

July 15, 2025

In the world of Linux and networking technologies, there are many subtle but critically important kernel settings. One such setting is rp_filter. This parameter, often overlooked, plays a key role in network security and correct packet routing. Let’s explore what it is, how it works, and why understanding it is essential for every system administrator.

What is rp_filter?

rp_filter stands for Reverse Path Filtering. It’s a Linux kernel mechanism that checks incoming network packets to verify whether they arrived on the interface through which a reply to the sender’s IP address would be routed.