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Flexible software routing with open source FRR

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Article from ADMIN 65/2021

By Benjamin Pfister

The FRR open routing stack can be integrated into many networks because it supports a large number of routing protocols, though its strong dependence on the underlying kernel means it requires some manual configuration.

In the past, many network administrators used pre-installed and expensive appliances for routing. Although this was used for a long time as a reliable solution, it is no longer suitable for more flexible use. For example, if you have highly virtualized server environments, the norm today, hardware appliances don't really make sense.

New approaches, such as network function virtualization (NFV) or software-defined networking (SDN), decouple networks from the hardware. Routing therefore needs to support integration into a service chain (i.e., the concatenation of the required services, alongside other functions such as firewalling or intrusion detection and prevention).

Moreover, it used to take a large amount of space, power, and money to learn in a test environment how routing protocols work with real hardware routers or to recreate specific behaviors. Network administrators who wanted to test their implementations for vulnerabilities had to build elaborate hardware environments or write their own routing stacks.

In this article, I look at an open routing stack provided by the open source project Free Range Routing [1], usually known as FRRouting or FRR.

Open Source Routing Stack Remedy

An open source routing stack can be an alternative to classic routers. In contrast, the conventional monolithic architectures with specialized application-specific integrated circuits (ASICs) or field-programmable gate arrays (FPGAs) for hardware-optimized packet forwarding obviously cannot directly offer the same performance optimizations; however, in some constellations, it is not so much a question of forwarding performance, but more likely about the functionality of the control plane, as when validating a network design. Control plane refers to the functions that can be used to control networks – Spanning Tree on Layer 2, for example,

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