FRRouting
Cumulus Linux uses FRRouting (FRR) to provide the routing protocols for dynamic routing and supports the following routing protocols:
- Open Shortest Path First (v2 and v3)
- Border Gateway Protocol - BGP
Architecture
The FRRouting suite consists of various protocol-specific daemons and a protocol-independent daemon called zebra. Each of the protocol-specific daemons are responsible for running the relevant protocol and building the routing table based on the information exchanged.
It is not uncommon to have more than one protocol daemon running at the same time. For example, at the edge of an enterprise, protocols internal to an enterprise (called IGP for Interior Gateway Protocol) such as OSPF text or RIP run alongside the protocols that connect an enterprise to the rest of the world (called EGP or Exterior Gateway Protocol) such as BGP.
About zebra
zebra is the daemon that resolves the routes provided by multiple protocols (including the static routes you specify) and programs these routes in the Linux kernel via netlink (in Linux). The FRRouting documentation defines zebra as the IP routing manager for FRRouting that “provides kernel routing table updates, interface lookups, and redistribution of routes between different routing protocols.”