Policy routing, also known as policy-based routing, refers to cases where the routing of traffic is based on criteria other than the destination network. A variety of criteria can be used to determine what route traffic takes, such as source or destination network, source or destination address or port, protocol, packet size, and many others. Basically, any criteria which can form the basis of a firewall rule can form the basis of policy routing. It is used often in multi-WAN setups, in cases where we want to direct traffic to a specific WAN interface based on certain criteria, but there are other cases where we might want to use policy routing as well.
You may recall in previous chapters, we sometimes had occasion to ...
