IP Virtual Server

IPVS (IP Virtual Server) implements transport-layer load balancing, usually called Layer 4 LAN switching, as part of the Linux kernel. It's configured via the user-space utility tool.
IPVS is incorporated into the Linux Virtual Server (LVS), where it runs on a host and acts as a load balancer in front of a cluster of real servers. IPVS can direct requests for TCP- and UDP-based services to the real servers, and make services of the real servers appear as virtual services on a single IP address. IPVS is built on top of the Netfilter.
IPVS is merged into versions 2.4.x and newer of the Linux kernel mainline.