Small To Medium-Sized Network Using Mixed Switches - Cisco Catalyst 3550 series Software Configuration Manual

Chapter 1 Overview
Network Configuration Examples

Small to Medium-Sized Network Using Mixed Switches

Figure 1-2 shows a configuration for a network of up to 500 employees. This network uses Catalyst 3550
multilayer switches to aggregate up to ten wiring closets through high-speed uplinks. For network
reliability and load balancing, this network includes two routers and two Catalyst 3550 multilayer
switches, all with HSRP enabled. This ensures connectivity to the Internet, WAN, and mission-critical
network resources if one of the routers or Catalyst 3550 multilayer switches fails.
The wiring closets have a mix of switches such as the Catalyst 3550, Catalyst 3500 XL, Catalyst 2950,
Catalyst 2900 XL, Catalyst 2820, and Catalyst 1900 switches. These switches are connected to
workstations, Cisco IP Phones, and local servers. You can cluster these switches into multiple clusters,
as shown, or into a single cluster. You can manage a cluster through the IP address of its primary and
secondary command switches, regardless of the geographic location of the cluster members.
This network uses VLANs to segment the network logically 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. You can have up to four VVIDs per wiring
closet. 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 are connected—using standard straight-through, twisted-pair cable with RJ-45
connectors—to the 10/100 inline-power ports on the Catalyst 3550-24PWR switches and to the 10/100
ports on the Catalyst 3550 switches. These multiservice switch ports automatically detect any IP phones
that are connected. Cisco CallManager controls call processing, routing, and IP phone features and
configuration. Users with workstations running Cisco SoftPhone software can place, receive, and control
calls from their PCs. Using Cisco IP Phones, Cisco CallManager software, and Cisco SoftPhone
software integrates telephony and IP networks, and the IP network supports both voice and data.
Each 10/100 inline-power port on the Catalyst 3550-24PWR switches provides 15.4 W per port. The
IP phone can receive redundant power when it is also connected to an AC power source. IP phones not
connected to the Catalyst 3550-24PWR switches receive power from an AC power source.
When an end station in one VLAN needs to communicate with an end station in another VLAN, a router
or multilayer switch routes the traffic to the appropriate destination VLAN. In this network, the
Catalyst 3550 multilayer switches provide inter-VLAN routing. VLAN access control lists (VLAN
maps) on the Catalyst 3550 switches provide intra-VLAN security and prevent unauthorized users from
accessing critical pieces of the network.
In addition to inter-VLAN routing, the Catalyst 3550 multilayer switches 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.
With the Catalyst 3550 multilayer switches providing inter-VLAN routing and other network services,
the routers focus on firewall services, Network Address Translation (NAT) services, voice-over-IP
(VoIP) gateway services, and WAN and Internet access.
Catalyst 3550 Multilayer Switch Software Configuration Guide
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