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Catalyst 3750 Switch Software Configuration Guide
OL-8550-09
Chapter 1 Overview
Network Configuration Examples
Figure 1-5 Linux Server Cluster
Small to Medium-Sized Network Using Catalyst 3750 Switches
Figure 1-6 shows a configuration for a network of up to 500 employees. This network uses a
Catalyst 3750 Layer 3 switch stack with high-speed connections to two routers. For network reliability
and load balancing, this network has HSRP enabled on the routers and on the switches. This ensures
connectivity to the Internet, WAN, and mission-critical network resources if one of the routers or
switches fails. The switches are using routed uplinks for faster failover. They are also configured with
equal-cost routing for load sharing and redundancy. (A Layer 2 switch stack can use cross-stack
EtherChannel for load sharing.)
The switches are connected to workstations, local servers, and IEEE 802.3af compliant and
noncompliant powered devices (such as Cisco IP Phones). The server farm includes a call-processing
server running Cisco CallManager software. Cisco CallManager controls call processing, routing, and
Cisco IP Phone features and configuration. The switches are interconnected through Gigabit interfaces.
This network uses VLANs to logically segment the network into well-defined broadcast groups and for
security management. Data and multimedia traffic are configured on the same VLAN. Voice traffic from
the Cisco IP Phones are configured on separate VVIDs. If data, multimedia, and voice traffic are
assigned to the same VLAN, only one VLAN can be configured per wiring closet.
When an end station in one VLAN needs to communicate with an end station in another VLAN, a router
or Layer 3 switch routes the traffic to the destination VLAN. In this network, the switch stack is
providing inter-VLAN routing. VLAN access control lists (VLAN maps) on the stack provide
intra-VLAN security and prevent unauthorized users from accessing critical areas of the network.
In addition to inter-VLAN routing, the multilayer switches provide QoS mechanisms such as DSCP
priorities to prioritize the different types of network traffic and to deliver high-priority traffic. If
congestion occurs, QoS drops low-priority traffic to allow delivery of high-priority traffic.