Improve Your Multi-Homed Servers with Policy Routing

Traditional IP routing systems route packets by comparing the destination address against a predefined list of routes to each available subnet; but when multiple potential routes exist between two hosts on a network, the preferred route may be dependent on context that cannot be inferred from the destination alone. The Linux kernel, together with the iproute2 suite, supports the definition of multiple routing tables and a routing policy database to select the preferred routing table dynamically. This additional expressiveness can be used to avoid multiple routing pitfalls, including asymmetric routes and performance bottlenecks from suboptimal route selection.