IP Virtual Server support will let you build a high-performance
virtual server based on cluster of two or more real servers. This
option must be enabled for at least one of the clustered computers
that will take care of intercepting incoming connections to a
single IP address and scheduling them to real servers.

Three request dispatching techniques are implemented, they are
virtual server via NAT, virtual server via tunneling and virtual
server via direct routing. The several scheduling algorithms can
be used to choose which server the connection is directed to,
thus load balancing can be achieved among the servers. For more
information and its administration program, please visit the
following URL: <http://www.linuxvirtualserver.org/>.

If you want to compile it in kernel, say Y. To compile it as a
module, choose M here. If unsure, say N.

source code:

net/ipv4/ipvs/