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LVS stands for “Linux Virtual Server“. LVS is a patched Linux kernel that adds a load balancing facility. For more information on LVS, please refer to the project homepage: http://www.linux-vs.org. LVS acts as a network bridge (using NAT) to load balance TCP/UDP stream. The LVS router components are:

  • WAN Interface: Ethernet Network Interface Controller that will be accessed by all the clients.
  • LAN Interface: Ethernet Network Interface Controller to manage all the load balanced servers.
  • Linux kernel: The kernel is patched with the latest LVS and is used as a router OS.

In this document, we will use the following keywords:

LVS Component

The Virtual IP is the IP address that will be accessed by all the clients. The clients only access this IP address.
Real server
A real server hosts the application accessed by client requests. WEB SERVER 1 & WEB SERVER 2 in our synopsis.
Server pool
A farm of real servers.
Virtual server
The access point to a Server pool.
Virtual Service
A TCP/UDP service associated with the VIP.

VRRP Component

The protocol implemented for the directors’ failover/virtualization.
IP Address owner
The VRRP Instance that has the IP address(es) as real interface address(es). This is the VRRP Instance that, when up, will respond to packets addressed to one of these IP address(es) for ICMP, TCP connections, ...
MASTER state
VRRP Instance state when it is assuming the responsibility of forwarding packets sent to the IP address(es) associated with the VRRP Instance. This state is illustrated on “Case study: Failover” by a red line.
BACKUP state
VRRP Instance state when it is capable of forwarding packets in the event that the current VRRP Instance MASTER fails.
Real Load Balancer
An LVS director running one or many VRRP Instances.
Virtual Load balancer
A set of Real Load balancers.
Synchronized Instance
VRRP Instance with which we want to be synchronized. This provides VRRP Instance monitoring.
The name of a simple VRRPv2 packet sent to a set of VRRP Instances while in the MASTER state.


Define RIP, DIP, Director, IPVS