Cisco Cisco IOS Software Release 12.2(18)SXF

IOS SLB provides the following routing features:

IOS SLB provides the following load-balancing algorithms:

You can specify one of these algorithms as the basis for choosing a real server for each new connection 
request that arrives at the virtual server.

For both algorithms, connections in closing state continue to be counted against the number of 
connections assigned to a real server. This impacts least connections more so than round robin, because 
the number of connections impacts the least connections more. IOS SLB adjusts the number of 
connections per real server, and the algorithm metrics, each time a connection is assigned.

The weighted round robin algorithm specifies that the real server used for a new connection to the virtual 
server is chosen from the server farm in a circular fashion. Each real server is assigned a weight, n, that 
represents its capacity to handle connections, as compared to the other real servers associated with the 
virtual server. That is, new connections are assigned to a given real server n times before the next real 
server in the server farm is chosen.

For example, assume a server farm comprised of real server ServerA with n = 3,  ServerB  with  n = 1,  and 
ServerC with n = 2. The first three connections to the virtual server are assigned to ServerA, the fourth 
connection to ServerB, and the fifth and sixth connections to ServerC.