Quagga

Quagga is an open-source implementation of various routing protocols. Its CLI resembles cisco syntax however do not expect it to be full cisco-like feature-rich router implementation.

Quagga is a fork and further reincarnation of Zebra routing suite, the demon communicating with kernel configuration and static routes is still carries its name - zebra.

Apart from zebra daemon, each routing protocol is implemented as separate daemon, having its separate config file and remote (telnet) management access.

To simplify management of various protocols under the same hood (on single server/router) one can use vtysh - a shell from which combined configuration could be managed - this mode most resembles cisco CLI.

Quagga implements multi-protocol version of BGP - BGP4 with RFC 2283 and RFC 4760, as well as multi-protocol OSPF v2 & v3 - RFC 2740.

You can look onto Quagga routing example to get its look and feel.