Network Warrior

How Server Load Balancing Works

Each of the previously listed Cisco load balancers is configured in a different way. Server load balancing (IP SLB) and CSMs are both configured similarly. I will concentrate on these technologies. For information regarding the Cisco CSS content switches or Local Directors, consult the Cisco documentation.

With IP SLB and CSM modules, SLB is implemented by creating a virtual server that is mapped to a logical server farm that contains physical real servers:

Virtual server

The virtual server is the IP address that will be used for accessing the services running on the real servers. The point of the virtual server is to make a single IP address appear to be a single server. The load-balancing system will then translate this single address, and forward the packets on to one of the server farms that have been bound to this virtual server.

Server farm

Server farms are logical groups of real servers.

Real server

A real server is a means of referencing the IP address of a physical server on the network. Real servers are grouped into one or more server farms. The server farms are then bound to one or more virtual servers.

This may seem needlessly complex, but consider the idea that you can have a real server in multiple server farms, and server farms assigned to multiple virtual servers. Let's say you have 100 real servers that are bound to a single virtual server. If you create 10 server farms, each containing 10 real servers, you'll be able to take 10 real servers ...