IPVS (IP Virtual Server) implements transport-layer load balancing inside the Linux kernel, so called Layer-4 switching. IPVS running on a host acts as a load balancer at the front of a cluster of real servers, it can direct requests for TCP/UDP based services to the real servers, and makes services of the real servers to appear as a virtual service on a single IP address.
1：get ipvsadm from http://www.linuxvirtualserver.org/software/ipvs.html#kernel-2.6
2: install kernel-devel ,ln -s /usr/src/kernel/xxxxx /usr/src/linux
3: popt-devel , libnl-devel, popt-static
4: install ipvsadm make && make install
or
yum install ipvsadm
detail info : http://kb.linuxvirtualserver.org/wiki/Compiling_ipvsadm_on_different_Linux_distributions
在 安装 keepalived出错时，同样需要执行【2、3】