General description
The network switch is the most common network device deployed with the enterprise infrastructure, and as such, selecting new switches or upgrading is a key part of most network design projects. Cisco network switch components include the switch chassis, supervisor engine, switch modules, IOS/CatOS software, and power supplies. The decision to purchase new switches or upgrade equipment will be made after considering network evaluation and specified design features. Wireless designs, for example, will have network switches that interface with access points. That will have an effect on the switch, such as increased utilization, assigned switch ports, access control lists, trunking, Spanning Tree Protocol, and increased Power over Ethernet (PoE) power consumption.
Change Chassis Features
Switch Chassis features include: chassis dimensions, number of slots, processor slot assignments, switch fabric, supported motor types, power supplies, rack units required.
Cisco Supervisor Engine (SE) Features
Cisco switches are implemented with an engine (switch processor) to process packets on a network segment. Routing is accomplished with either an integrated multilayer switch function card (MSFC) or a routing processor running the IOS code. The Switch Engine running IOS code on MSFC and the Switch Processor are in native mode, while those running CatOS on the processor are in hybrid mode. Some engines will not support native and hybrid mode. The non-MSFC engine supports what is called CatOS mode. Select the motor that matches your design specifications. The MSFC module is integrated with the engine or can be upgraded. You must implement a PFC module with any MSFC. Some engines do not have an MSFC module – routing is built in with the hardware and as such only supports native mode.
Cisco Supervisor Engine features include: supported chassis, uplink speed, processor memory, native IOS, CatOS, PFC, MSFC, slot allocation, failover.
These are some of the popular Cisco engines and their switching features.
720 – Cisco 6500 Switches, 400 mpps, MSFC3, IOS, CatOS
32 – Cisco 6500 Switches, 15 mpps, MSFC2A, IOS, CatOS
V – Cisco 4500 Switches, 72 mpps, Integrated Routing, IOS
IV – Cisco 4500 Switches, 48 mpps, Integrated Routing, IOS
Switch Module Features
Switch module features include: supported switch chassis, interface speed, number of ports, media, cabling, connectors, throughput (mpps), supported supervisor engines, protocol features, Power over Ethernet (Cisco pre-standard or 802.3af).
– Media: Copper, Fiber
– Cabling: UTP Cat 5, CAT 5e, CAT 6, STP, MMF, SMF
– Connectors: RJ45, RJ21, SC, LC
– Transceivers: GBIC, SFP
Power Supply Features
Power supply features include: supported chassis, power rating, failover, input/output amps, power cord type, IOS, CatOS.
IOS/CatOS software
Cisco network switches can be deployed with IOS, IOS and CatOS, or with proprietary CatOS software. Design features will determine which mode and version of IOS or CatOS is selected. The software running on the Route Processor must be IOS, while the Engine Switch Processor will run IOS (native mode) or CatOS (hybrid mode). Some Cisco equipment, such as the 4507R, implement Supervisor Engine IV with no embedded MSFC. The Route Processor is integrated with the engine. With that design, Engine IV does not support CatOS.
Native IOS – Deployed at the edge of the network, where most of the routing happens and some switching is needed
Hybrid – Deployed at the core of the network where there is high-speed routing and switching
CatOS – Deployed at the network access layer where there is switching and no routing
Switch selection process:
The following are the 5 components of any network switch selection process:
1. Consider the evaluation of the network and the specified design characteristics
2. Select switches that include all design features
3. Select switches with the right scalability
4. Balance equipment cost and features while meeting budget guidelines
5. Select IOS and/or CatOS software version
Network evaluation and design specifications should be considered before selecting any network switch. The network assessment examines the design, configuration, and equipment that is deployed in the office where the selected devices will be deployed. The design specifications will determine the necessary performance, availability, and scalability characteristics. The selection of the IOS and/or CatOS version occurs after deciding on the feature set. Businesses will specify a budget and that is a key consideration with any equipment selection. It is not cost effective to select a Cisco 6509 switch for an office with 50 employees. It is important that you select equipment that meets your design specifications, has the necessary scalability features, and meets your budget guidelines.
Some typical characteristics of switches to consider:
1) Are there enough chassis slots?
2) What supervisor engines are supported?
3) Does the engine support failover?
4) Is multilayer switching available?
5) What switch modules are available?
6) What uplinks are available?
7) What power supply power is available?
8) How many Rack Units are needed?
Switch selection example:
The network assessment discovered the following at the company’s office.
The Distribution Office has 300 employees
Fast Ethernet (100BaseT) is implemented on the desktop
Cisco 6509 Switches with Gigabit Ethernet Trunking
Cisco 3800 Router with Dual T1 Circuits
Power over Ethernet is implemented
Multiple VLANs defined
Local Unix and Windows servers
Some bandwidth intensive applications
IP Telephony is implemented in all offices
Wiring closets are 500 feet apart
Multiple Rack Units are available in the Rack Cabinet
The design specifies that 180 more people will soon be employed. The company will have those employees working from a third floor where the closest wiring closet is within 500 feet of the Cisco 6509. The company will implement some wireless IP telephony and define VLANs with each specific company department.
The following is a list of specific switching functions required:
1. 4-slot chassis with 48-port switch modules – 10/100BaseT
2. Gigabit Ethernet trunk between wiring closets
3. Failover Supervisor Engines
4. Multilayer switching
5. Support Power over Ethernet
6. Dual power supplies with at least 2800 W for IP phones
7. Quality of Service for IP Telephony
8. Performance switching for converged telephony network
Selected switch: Cisco 4507R
The Cisco 4507R switch has 7 slots and is a good selection with the additional 180 employees. The device will have modules from 4 to 48 ports with one slot available for any additional employees. The dual IV engines will be allocated 2 slots with failover, multi-layer switching between VLANS and Gigabit Ethernet uplinks connecting the 6509 devices. Each of the switch modules is PoE capable with the new 802.3af standard. Dual power supplies provide enough power to deploy hundreds of Cisco IP phones and wireless access points. Engine performance is 75 mpps with wire speed change. The Cisco 4507R is more cost effective than the closest Cisco 6509 device. Several engine models are available with additional performance features.
– 7-slot chassis with 2 Supervisor Engines and 4 Switching Modules with 48 Ports – 10/100BaseT
– Engine IV with integrated multilayer switching, failover, dual Gigabit uplinks
– Support for Power over Ethernet (PoE) with the 802.3af standard
– Dual power supplies with 2800 W or 4200 W for telephony, wireless, Power over Ethernet
– Quality of service functions for voice traffic
– Fast performance with 75 mpps wire speed switching for converged networks
The Cisco 3750 series switch was not that expensive; however, there weren’t enough slots, the stacking technology is expensive, and the switches have a speed of 38.7 mps compared to the 75 mps 4507R device. The company would have to purchase 5 separate 48-port switches for 180 employees. The Cisco 2950 switch does not have failover or power supply scalability. The 6509 switch was much more expensive, had 2 extra slots, more performance than necessary, and the switch modules were expensive. Implementation is somewhat difficult with Cisco 6500 devices.
