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Modular switches: advantages and disadvantages

… or why modular switches could enjoy a renaissance

Modular switches refers to network switches that are built in a medium to very large chassis.  Cisco built thousands of Catalyst 6500 series. Extreme has the BlackDiamond series.  HPE is known for their 5400zl series. Arista has their high performance 7504 and 7508 series.  It is kind of like having a big chest or drawers and then selecting what kind of drawers go into each slot. These modular chassis switches were produced in large numbers in the mid-to-late 2000s and dominated many corporate and data center cabinets until the advent of stackable switches.

The dominating frustration with the modular chassis in the early 2000s was that it was “big, clunky, expensive, required a network cabinet with accompanying cooling system and heavy power requirements.”  For anyone transitioning for normal traditional box style switches with 48 ports, the complaint was valid.

Many of these switches ended up at remote data centers power servers with a side-of-rack wiring systems.  If they were used in the corporate environment, the Cat5E/6 wiring always looked like a spaghetti dinner with too many spices.

The heavy demand to buy the modular chassis switch went away with the advent of the stackable switch. Most network managers asked the same question: why would one want to spend time, money and space on these big chasses when one could buy traditional 24 and 48 port switches and stack them together?

To anyone that owns and manages a chassis switch, the advantages for any firm are huge:  flexibility, multiple functions, rapid expansion, lower cost per port pricing, plethora of chassis and module options.

Advantage #1:  Flexibility

Modular Switch - Cisco VS-S2T-10G Supervisor Engine
Cisco VS-S2T-10G Catalyst 6500 Series Supervisor Engine 2T Switch Module – still going strong!

As your business changes, so do your network requirements, including networking switches.  Stackable switches are generally limited to stacking within the same model family and having the same firmware.  Because of that limitation, a “stack” of normal or traditional switches can only provide you with switching capacity.  They are limited in security and other facets.  To upgrade speed and capacity, one must change out the entire stack of switches.

Unlike traditional switches, modular switches are network switches that can be modified using replaceable units as the business requirements change. You can add or remove modules into the switches, resulting in improved flexibility for your varying network needs.  As technology advances, one can change out a supervisor engine such as a Cisco VS-S2T-10G (the board that controls and manages the chassis) and increase performance on all network ports on the chassis.

The most significant advantage of adopting modular switches is the increased flexibility they provide. Depending on the requirements, switch modules such as a Cisco WS-X6816-10G-2T can be simply added from the network infrastructure with ease. The expansion modules, including supervisor engines, line cards (modules with network ports), power supplies, or cooling fans, can be added or removed. If you have a large enough chassis such as a Cisco WS-C6513 – a chassis with 13 slots – one could easily expand the ports available as your corporate needs expand.

Advantage #2: Multiple functions

Stacked switches have limited ability to offer enhanced network security features.  Manufacturers are working to bring more network security options to each device but these options are limited in comparison to what a dedicated security device can offer.

Modular switches offer an option of adding a dedicated network security device on a module of the chassis.  Instead of being limited to simply a stack of switches, a modular switch can have multiple roles.  Cisco 6500 series also offers modules to manage wireless access points such as the Cisco WS-SVC-WISM2-1-K9.

Advantage #3: Rapid increase in network ports

With a sufficiently large enough chassis, one has a much easier way of adding network capacity rapidly and without much effort.  A 13 module slot chassis could in theory have 12 48 port switch modules offering 576 network ports.  If one buys a chassis with more slots than one needs initially, one will find an easier upgrade path that adding more stacked switches.

Advantage #4: Cost per port

Modular Switch - Cisco WS-X6816-10T-2TXL Line Card
Cisco WS-X6816-10T-2TXL Catalyst 6500 16x 10GB Copper Switch Module w/ DFC4XL

Didn’t we just say above that one of the big complaints with modular switching was the cost?  We did. But the cost has gone way down.  There is also a surplus of secondary market equipment available that is driving this pricing drop.  With modular network switches, you are provided with a pay-per-use model. This means that you won’t be spending unnecessary finances on the network infrastructure or operation and maintenance. Although the initial investment for this flexible switching infrastructure is slightly more than normal traditional switches, the savings is in the upgrade and managing any replacements.

Also, as the demand decreased for modular switches, the cost for ever increasing port speed decreased.  Cisco WS-X6716-10T-3C 10GB modules are much more affordable.  Gigabit port speed modules such as the Cisco WS-X6748-GE-TX are very inexpensive per port.

Advantage #5: Plethora of chassis and module options

With modular switches, you get a variety of options based on your requirements and financial capabilities. They are available in entry-level, mid-range, and high-end modular options for every business’s unique needs.

On top of the stacking options, you can also choose to have mix-n-match ports as per your requirements. These switches allow you to combine copper, fiber, and PoE ports and add it seamlessly to your organization’s network. You can also collaborate with your vendor to create a package tailored to your needs.

You need to find answers to numerous questions before buying network switches for your company. The final decision to choose the optimal network switches ultimately depends on your business requirements and how quickly you want to scale. However, if you are looking for modifications-on-the-go to live up to the changing customer expectations and business needs, it would be best if you opted for modular switches over fixed ones.

HPE J8698A Modular Switch
HPE J8698A 5400zl Series ProCurve 5412zl Intelligent Edge Switch

Mike Syiek
Mike Syiek
Mike Syiek is President and Founder of NetworkTigers.

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