Server Load Balancing (Slb) - Cisco Catalyst 2000 Configuration Handbook

Server Load Balancing (SLB)

See the following sections to configure and use these features:
■ 10-1: SLB: Covers the configuration steps needed to provide load balancing of traffic
to one or more server farms
10-2: SLB Firewall Load Balancing: Discusses the configuration steps necessary to
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load balance traffic to one or more firewall farms
10-3: SLB Probes: Explains the configuration steps needed to define probes that test
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server and firewall farm functionality
10-1: SLB
SLB provides a virtual server IP address to which clients can connect, representing a
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group of real physical servers in a server farm. Figure 10-1 shows the basic SLB con-
cept. A client accesses a logical "virtual" server (IP address v.v.v.v), which exists only
within the Catalyst 6500 SLB configuration. A group of physical "real" servers (IP ad-
dresses x.x.x.x, y.y.y.y, and z.z.z.z) is configured as a server farm. Traffic flows be-
tween clients and the virtual server are load balanced across the set of real servers,
transparent to the clients.
As clients open new connections to the virtual server, SLB decides which real server
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to use based on a load-balancing algorithm.
Server load balancing is performed by one of these methods:
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Weighted round-robin: Each real server is assigned a weight that gives it the
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capability to handle connections, relative to the other servers. For a weight n, a
server is assigned n new connections before SLB moves on to the next server.
■ Weighted least connections: SLB assigns new connections to the real server
with the least number of active connections. Each real server is assigned a
Chapter 10