BIRD！！！！！

DreamCat

官方站点：http://bird.network.cz/

There already exist other such routing daemons: routed (RIP only), GateD http://www.gated.org/ (non-free), Zebra http://www.zebra.org and MRTD http://www.zcu.cz/ftp/mirrors/mmrz/mrtd, but their capabilities are limited and they are relatively hard to configure and maintain.

BIRD is an Internet Routing Daemon designed to avoid all of these shortcomings, to support all the routing technology used in the today's Internet or planned to be used in near future and to have a clean extensible architecture allowing new routing protocols to be incorporated easily. Among other features, BIRD supports:

• both IPv4 and IPv6 protocols (use --enable-ipv6 when configuring)
• multiple routing tables
• the Border Gateway Protocol (BGPv4)
• the Routing Information Protocol (RIPv2)
• the Open Shortest Path First protocol (OSPFv2) (IPv4 only)
• a virtual protocol for exchange of routes between different routing tables on a single host
• a command-line interface allowing on-line control and inspection of status of the daemon (using the `birdc' client; to get some help, just press `?')
• soft reconfiguration (no need to use complex online commands to change the configuration, just edit the configuration file and notify BIRD to re-read it and it will smoothly switch itself to the new configuration, not disturbing routing protocols unless they are affected by the configuration changes)
• a powerful language for route filtering

BIRD has been developed at the Faculty of Math and Physics, Charles University, Prague, Czech Republic as a student project. It can be freely distributed under the terms of the GNU General Public License. BIRD has been designed to work on all UNIX-like systems. It has been developed and tested under Linux 2.0 to 2.4, and then ported to FreeBSD and NetBSD, porting to other systems (even non-UNIX ones) should be relatively easy due to its highly modular architecture.

hb2k

即便跑得动，也没人敢往骨干网上接的。作nat/pat转换还是比较有优势。

DreamCat

的确如此，不过作为中小型企业用还是可以的，结合NAT，VPN以及其他一些功能，功能还是很强的，实际的使用例子似乎是邮电系统用的最多。