Specifications

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Catalyst 2970 Switch Software Configuration Guide
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Chapter 1 Overview
Network Configuration Examples
Small to Medium-Sized Network Using Catalyst 2970 Switches
Figure 1-3 shows a configuration for a network of up to 500 employees. This network uses Catalyst 2970
switches with high-speed connections to two routers. For network reliability and load balancing, this
network has HSRP enabled on the routers. This ensures connectivity to the Internet, WAN, and
mission-critical network resources in case one of the routers fails. The switches are using EtherChannel
for load sharing.
The switches are connected to workstations, Cisco IP Phones, and local servers. 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. For any switch port connected to Cisco IP Phones, 802.1P/Q QoS gives
voice traffic forwarding-priority over data traffic. Cisco IP Phones not connected to Catalyst Power over
Ethernet (PoE) switches must be connected to AC power sources to receive power.
When an end station in one VLAN needs to communicate with an end station in another VLAN, a router
routes the traffic to the appropriate destination VLAN. In this network, the routers are providing
inter-VLAN routing. VLAN access control lists (VLAN maps) provide intra-VLAN security and prevent
unauthorized users from accessing critical pieces of the network.
In addition to inter-VLAN routing, the routers provide QoS mechanisms such as DSCP priorities to
prioritize the different types of network traffic and to deliver high-priority traffic in a predictable manner.
If congestion occurs, QoS drops low-priority traffic to allow delivery of high-priority traffic.
The routers also provide firewall services, Network Address Translation (NAT) services, voice-over-IP
(VoIP) gateway services, and WAN and Internet access.
Figure 1-3 Catalyst 2970 Switches in a Collapsed Backbone Configuration
Gigabit
servers
89375
Cisco 2600 or
3700 routers
Catalyst 2970
switches
Internet
Cisco IP
phones
Workstations
running
Cisco SoftPhone
software
Aironet wireless
access points
IP IP