Linux has been a first class networking citizen for quite a long time now. Every box running a Linux kernel out of the box has at least three routing tables and is supporting multiple mechanisms for advanced routing features from policy based routing (PBR), to VRFs(-lite), and network namespaces (NetNS). Each of these provide different levels or separation and features, with PBR being the oldest one and VRFs the most recent addition (starting with Kernel 4.3).
This article is part of the Linux Routing series and will provide an overview on Policy-based routing (PBR) and its applications. The previous post about Linux Routing Fundamentals covers the basics and plumbings of Linux routing tables, what happens when an IP packet is sent from or through a Linux box, and how to figure out why. It is a good read if you don’t feel familiar with these topics. Posts about VRFs and Network Namespaces will follow.
Continue reading Advanced Linux Routing – Policy-based routing