gobgp

GoBGP is BGP without the hardware router. BGP is the protocol that decides how traffic moves between networks, and historically you ran it on a Cisco or Juniper box or a heavyweight legacy daemon. GoBGP is a clean, modern implementation written from scratch in Go that runs as a standalone daemon or, more interestingly, as a library you drive over a gRPC API. That makes it the go-to when you want to build BGP control into your own software: route injection, SDN controllers, anycast automation.

The install is easy, a single Go binary and a config file. Operating it is not. BGP is unforgiving, and peering, route policy, and filtering still demand real networking knowledge no matter how clean the tool is. It supports the features that matter in production: route reflection, EVPN, flowspec, RPKI, and Zebra integration.

It is Apache-2.0 and entirely free, with no paid tier. For a plain software router, FRRouting and BIRD are the usual alternatives and have broader feature sets for traditional routing. GoBGP wins when you want BGP as a programmable building block rather than a box you configure. Solo, small, or large team: the cost is your time and expertise, not a license.

The catch is that a BGP mistake does not throw an error, it silently moves traffic. The tooling cannot save you from a bad policy, and the ecosystem around GoBGP is smaller than FRR's, so you will lean on the docs and the source more than on Stack Overflow.