computer networking A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

, policy-based routing (PBR) is a technique used to make

routing Routing is the process of selecting a path for traffic in a network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit-switched networks, such as the public switched telephone netw ...

decisions based on policies set by the network administrator. When a router receives a packet it normally decides where to forward it based on the destination address in the packet, which is then used to look up an entry in a

routing table In computer networking, a routing table, or routing information base (RIB), is a data table stored in a router or a network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with th ...

. However, in some cases, there may be a need to forward the packet based on other criteria. For example, a network administrator might want to forward a packet based on the source address, not the destination address. This permits routing of packets originating from different sources to different networks even when the destinations are the same and can be useful when interconnecting several private networks. Policy-based routing may also be based on the size of the packet, the protocol of the payload, or other information available in a packet header or payload. In the

Cisco IOS The Internetworking Operating System (IOS) is a family of proprietary network operating systems used on several router and network switch models manufactured by Cisco Systems. The system is a package of routing, switching, internetworking, and ...

, PBR is implemented using ''route maps''. Linux supports multiple routing tables since version 2.2.Linux Advanced Routing & Traffic Control HOWTO
/ref> FreeBSD supports PBR using either IPFW, IPFilter or OpenBSD's PF.

Examples

PBR can be used to redirect traffic to a proxy server by using a PBR-aware L3-switch (router). In such deployment, specific source traffic (e.g. HTTP, FTP) can be redirected to a cache engine. This is known as virtual inline deployment.

Notes

References

External links

Policy routing Cisco Press article

Network overview by Rami Rosen
Routing {{network-stub