Network Switch Selection – How to Select a Network Switch

Overview

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 consideration of the 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 higher utilization, assigned switch ports, access control lists, trunking, spanning tree protocol, and higher Power over Ethernet (PoE) power consumption.

Change chassis features

Switch Chassis features include: chassis dimensions, number of slots, processor slot assignments, switch fabric, motor types supported, 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 an integrated Multilayer Switch Function Card (MSFC) or routing processor running IOS code. The Switch Engine running IOS code on the MSFC and the Switch Processor is 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 – the routing is integrated 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 mapping, failover.

Here 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

– Wiring: UTP Cat 5, CAT 5e, CAT 6, STP, MMF, SMF

– Connectors: RJ45, RJ21, SC, LC

– Transceivers: GBIC, SFP

Power supply characteristics

Power supply features include: supported chassis, power rating, failover, input/output amps, power cord type, IOS, CatOS.

Software IOS/CatOS

Cisco network switches can be implemented 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, implements the Supervisor Engine IV without an integrated MSFC. The Route Processor is integrated with the engine. With that design, Engine IV is not compatible with CatOS.

Native IOS – Deployed at the edge of the network, where most routing occurs and some switching is needed

Hybrid: Deployed at the core of the network where there is high-speed routing and switching

CatOS – Implemented at the network access layer where there is switching and no routing

Switch selection process:

The 5 components of any network switch selection process are outlined below:

1. Consider network evaluation and specified design features

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 must 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 required performance, availability, and scalability characteristics. IOS and/or CatOS version selection occurs after deciding on the feature set. Companies 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’s important that you select computers that meet your design specifications, have the necessary scalability features, and meet 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 multi-layer switching available?

5) What switching 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 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

Various Rack Units are available in the Rack Cabinet

The design specifies that an additional 180 people will soon be employed. The company will have those employees working from a third floor where the closest wiring closet is 500 feet from the Cisco 6509. The company will implement some wireless IP telephony and define VLANs with each specific department in the company.

The following is a list of specific switching functions required:

1. 4 chassis slots with 48-port switch modules – 10/100BaseT

2. Gigabit Ethernet trunk link between wiring closets

3. Supervisor Engines with failover

4. Multi-layer switching

5. Support Power over Ethernet

6. Dual power supplies with at least 2800W for IP phones

7. Quality of Service for IP Telephony

8. Switching performance 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. Dual IV engines will be allocated 2 slots with failover, multi-layer switching between VLANS, and Gigabit Ethernet uplinks connecting 6509 devices. Each of the switching 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. Motor performance is 75 mpps with wire speed change. The Cisco 4507R is more cost effective than the closest Cisco 6509 device. Various 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 features for voice traffic

– Fast performance with 75 mpps wire-speed switching for converged networks

The Cisco 3750 series switch wasn’t that expensive; however, there were not enough slots, the stacking technology is expensive, and the switches are clocked at 38.7 mps compared to the 4507R’s 75 mps. The company would have to purchase 5 separate switches with 48 ports for 180 employees. The Cisco 2950 switch does not have power supply failover or scalability. The 6509 switch was much more expensive, had 2 extra slots, more throughput than needed, and the switch modules were expensive. Deployment is somewhat difficult with Cisco 6500 devices.