Cisco Catalyst 4948 User Manual

Chapter 10
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
load balance traffic to one or more firewall farms
■ 10-3: SLB Probes: Explains the configuration steps needed to define probes that test
server and firewall farm functionality
10-1: SLB
■ SLB provides a virtual server IP address to which clients can connect, representing a
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
to use based on a load-balancing algorithm.
■ Server load balancing is performed by one of these methods:
■ Weighted round-robin: Each real server is assigned a weight that gives it the
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

Cisco Catalyst 4948 Specifications

General

Switching Capacity	136 Gbps
Forwarding Rate	102 Mpps
Rack Units	1U
MAC Address Table Size	32, 000 entries
Authentication Method	RADIUS, TACACS+
RAM	256 MB
Flash Memory	64 MB
Power Device	Internal power supply
Voltage Required	100-240 VAC
Weight	16.5 lbs
Operating Humidity	10% to 85% non-condensing
Ports	48 x 10/100/1000
Power Supply	Internal
Layer Support	Layer 3
Jumbo Frame Support	Yes (up to 9216 bytes)
Routing Protocol	RIP, OSPF, EIGRP, BGP
Remote Management Protocol	SNMP, Telnet, SSH
Features	VLAN support, QoS
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.3ab, IEEE 802.1Q, IEEE 802.1p
Operating Temperature	32 °F to 104 °F (0 °C to 40 °C)