XORP

"XORP is a modular, extensible, open source networking platform that can be leveraged by:

• Network operators wanting to reduce cost by running open source networking applications on off-the-shelf hardware.
• Network equipment vendors wanting to expand market presence for their special-purpose hardware.
• Network application writers vendors wanting to expand market presence for their special purpose hardware.
• Network researchers wanting a platform for experimentation and invention. 

XORP code can be downloaded and used to build a fully functional PC-based router. A basic implementation of XORP is also available as a Live CD--i.e, a downloadable CD image that can be burned to a bootable CD. This allows XORP to be run without installing any additional software, understanding how XORP works internally, or knowing anything about Linux/Unix system administration.

XORP has a single unified command line interface (CLI) which is used to configure routing protocols and network interfaces. XORP's CLI can be extended to encompass additional router functionality such as queue manangement, QoS configuration, firewalls, NATs and DHCP configuration. The XORP architecture also permits different routing protocols to run in different security "sandboxes", offering the potential for greater robustness and security than alternative router platforms.

XORP currently supports both IPv4 and IPv6 versions of BGP4+, OSPFv2, OSPFv3, RIP and RIPng for unicast routing, and PIM-SM and IGMP/MLD for multicast. XORP runs on most Linux and *BSD distributions."

http://www.xorp.org/

http://www.read.cs.ucla.edu/click/projects