What is Keepalived ?

The main goal of the keepalived project is to add a strong & robust
keepalive facility to the Linux Virtual Server project. This project
is written in C with multilayer TCP/IP stack checks. Keepalived
implements a framework based on three family checks: Layer3, Layer4
& Layer5/7.

This framework gives the daemon the ability of checking a LVS server
pool states. When one of the server of the LVS server pool is down,
keepalived informs the linux kernel via a setsockopt call to remove
this server entrie from the LVS topology. In addition keepalived
implements an independent VRRPv2 stack to handle director failover.
So in short keepalived is a userspace daemon for LVS cluster nodes
healthchecks and LVS directors failover.