Perroute

Perroute is a term used in computer networking to describe the practice of applying routing decisions and associated policies on a per-route basis. It refers to routing where different routes can have distinct handling rules within a single device, across a network segment, or within a software-defined network. Perroute approaches typically build on policy-based routing concepts, enabling finer-grained control over forwarding behavior than traditional destination-based routing.

Key ideas behind perroute include the use of multiple routing tables, route maps or policy rules, and per-route attributes such as next hop, metrics, Quality of Service, firewalling, or NAT. In traditional routers, this is implemented through route maps, access control lists, and policy routing configurations that direct traffic into specific routing tables. In Linux environments, policy routing is achieved with tools like ip rule and ip route, which assign traffic to alternative routing tables based on criteria such as source address, destination, or traffic class. In software-defined networking, perroute rules can be implemented via flow-based policies and controller-directed rules.

Common use cases include traffic engineering, cost management, and high-availability setups where certain traffic (for example, VoIP or critical applications) must follow a preferred path, while non-critical traffic uses an alternative path. Perroute can enable improved performance, fault tolerance, and policy compliance but adds configuration complexity and potential for misrouting if rules are not carefully managed.

Related concepts include policy-based routing, route maps, QoS, NAT, and SDN-enabled per-flow routing.