What is rp_filter and what is it used for?

2025-07-15

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.