In 2003, a group of developers decided to pursue a Zebra code fork later named the Quagga Project (http://www.quagga.net). The protagonists of the Quagga Project opted for a fork to provide a more dynamic release cycle, greater community involvement, rapid acceptance of community feedback, and quick incorporation of critical patches. Changes to Zebra will be incorporated into Quagga as well. The Quagga website provides much more documentation and example configurations than the Zebra website. Installation and configuration work exactly as described in the Zebra section. However, Quagga supports additional configuration options that you can display by typing ./configure --help. I am using the following sequence in my setups:
./configure --enable-vtysh --enable-netlink --enable-snmp
--enable-tcp-zebra --enable-nssa --enable-opaque-lsa
--enable-ospf-te --enable-multipath=6 --with-libpam
This requires that a quagga group and quagga user are configured on the system (present in /etc/passwd and /etc/groups).
With regard to the configuration examples, it should not make a difference whether you are using Quagga or Zebra. However, many bugs have been fixed in Quagga that are still present in the Zebra code. Some innovations such as route servers are only present in Quagga code. Note that recently another IS-IS daemon was integrated into Quagga that is different from the code available for Zebra (but is actually based on it).