Understanding the campus size and traffic is an important factor in network design. A large campus is defined as several or many colocated buildings, and a medium campus is one or more colocated buildings. Small campus networks have only one building.
By understanding your campus size, you can choose Cisco products that will fit your business needs and grow with your company. Cisco switches are produced to fit neatly within its three-layer model. This helps you decide which equipment to use for your network efficiently and quickly.
It should be noted that the Cisco range of switches is in a transitional phase between two operating systems. The Catalyst Operating System (CatOS) is the traditional method and is often referred to as using set commands because when configuring, the command often begins with the word “set.” Switches in this line include the 4000 and the 6000/6500.
The switches based on the IOS are called Catalyst IOS (CatIOS) switches. The interface to configure these switches resembles that of the IOS router but isn’t entirely the same. Anyone familiar with configuring a router, though, will be comfortable configuring one of these switches. The switches that use this include the 2950, the 3550, and the 8500 series.
With some switches—for instance, the 6000/6500 series—you have a choice between the two types of operating systems. When this occurs, the CatOS is the default OS.
Cisco Express Forwarding (CEF) allows for real layer 3 switches to forward traffic based on a complete layer 3 topology map. This map is shared with the ASICs at each port, enabling each port to know which port a packet should be forwarded to. Rather than forwarding based on MAC address, forwarding is done by layer 3 address. Only switches that have true layer 3 capabilities can do this type of switching. These devices include the 3550 series, the 4000 series, the 6000/6500 series with PFC2, and the 8500 series.
There are two general rules when it comes to Cisco switches: The lower model numbers usually cost less, and purchasing a device with more ports drives down the per-port cost. In addition, the model number may typically be split into two sections: For slot-based switches, the second number usually refers to the number of physical slots it has. The 6509 is a nine-slot device in the 6500 family of switches.
The access layer, as you already know, is where users gain access to the internetwork. The switches deployed at this layer must be able to handle connecting individual desktop devices to the internetwork. The switches here are usually characterized as having a large number of ports and being low cost. Most access switches don’t have a lot of frills.
The Cisco solutions at the access layer include the following:
2950 Provides switched 10/100 Mbps to the desktop. All ports are capable of full duplex, and options include Gigabit Ethernet interfaces. The standard Cisco IOS means that the switch supports functionality for basic data, video, and voice services. All Catalyst 2950 and 2955 switches also support the Cisco Cluster Management Suite (CMS) Software, which allows users to use a standard web browser to simultaneously configure and troubleshoot multiple Catalyst desktop switches.
3550 Provides a range of stackable selections that can be used as access switches with the Standard Multilayer Software Image (SMI). Many options are available, including 24 and 48 ports, inline power for IP telephony, and a range of 10/100/1000Mbps ports.
If power for IP phones is required but a switch with inline power is not available, Cisco also has a product called the “Inline Power Patch Panel” that adds inline power to an existing Catalyst switch.
4000 Provides a 10/100/1000Mbps advanced high-performance enterprise solution for up to 96 users and up to 36 Gigabit Ethernet ports for servers. Some models also support the delivery of inline power for IP telephones.
As discussed earlier, the primary function of the distribution layer is to provide routing, filtering, and WAN access and to determine how packets can access the core, if needed.
Distribution layer switches are the aggregation point for multiple access switches and must be capable of handling large amounts of traffic from these access layer devices. The distribution layer switches must also be able to participate in MLS and be able to handle a route processor.
The Cisco switches that provide these functions are as follows:
3550 Series This range includes a variety of stackable switches supporting a huge range of features. Full IOS operation complete with MLS is available, and this makes the switch suitable for both access layer and distribution layer switching.
4000 Series One of the most scalable switches, the 4000 can be used as a distribution switch if the supervisor IV engine supporting MLS is installed. The 4000 series support advanced QoS, security, and flexibility, achieved with a range of modules. Numerous chassis are available, providing advanced features such as non-blocking architecture and resilience through redundant supervisors. This range has been given a real boost by Cisco.
6000 The Catalyst 6000 can provide up to 384 10/100Mbps Ethernet connections, 192 100FX FastEthernet connections, or 130 Gigabit Ethernet ports. (With the recent release of the 10/100/1000 card, the 6500 can now support up to 384 10/100/1000 Ethernet connections.) In addition to regular connections, IP telephone connections with inline power are also supported. The 6000 can be outfitted with a Multi-layer Switch Feature Card (MSFC) to provide router functionality as well as a Policy Feature Card (PFC) for layer 3 switching functionality.
The core layer must be efficient and do nothing to slow down packets as they traverse the backbone. The following switches are recommended for use in the core:
6500 The Catalyst 6500 series switches are designed to address the need for gigabit port density, high availability, and multi-layer switching for the core layer backbone and server-aggregation environments. These switches use the Cisco IOS to utilize the high speeds of the ASICs, which allows the delivery of wire-speed traffic management services end to end.
8500 The Cisco Catalyst 8500 is a core layer switch that provides high-performance switching. The Catalyst 8500 uses ASICs to provide multiple-layer protocol support including IP, IP multicast, bridging, ATM switching, and policy-enabled QoS.
All these switches provide wire-speed multicast forwarding, routing, and Protocol Independent Multicast (PIM) for scalable multicast routing. These switches are perfect for providing the high bandwidth and performance needed for a core router. The 6500 and 8500 switches can aggregate multiprotocol traffic from multiple remote wiring closets and workgroup switches.