A stackable switch brings value to the wiring closet

A fixed configuration, stackable switch can offer a lower price per port over its modular counterparts.

Stackable switches are the workhorses of the enterprise campus network. These fixed configuration switches offer the endpoint connectivity and uplink capabilities that enterprises need at a price per port that is much lower than modular switching products. Whether an enterprise outfits its wiring closets with stackable switches will depend on what services are needed and how much redundancy is required at the network edge.

A fixed configuration switch, as its name suggests, is a standalone Ethernet switch in a self-contained enclosure. While modular switches offer the ability to swap line cards or service modules in and out as needed, a fixed configuration switch is limited to the ports and interfaces that the manufacturer shipped it with.  Fixed configuration switches ship with 12, 24 or 48 Gigabit Ethernet (GbE) ports, and either 10 GbE or optical uplink ports. Networking vendors also offer a choice of Power over Ethernet (PoE) or non-PoE stackable switches. Unless an organization requires high-end functionality in its edge switches, such as wirelss LAN controllers, firewall security or high availability, the difference between modular and stackable switch largely comes down to price.

This lack of physical expandability is ultimately what lowers the cost of a stackable switch, making it an excellent choice for the access layer of an enterprise network. Enterprises can cheaply fill their wiring closets with fixed configuration, stackable switches to provide network access and PoE to desktops, IP phones and other network devices at the edge.

Stackable switches: What do you get in a stack?

Stacking multiple fixed configuration switches together is a simple matter of daisy-chaining multiple switches one after the other, with the last switch in the stack connecting back to the first, creating a complete loop within the stack. The loop from the final switch to the first is particularly important, as it keeps the stack connected, even if one of the switches in between suffers a hardware failure.

A stack of fixed configuration switches can resemble its modular counterparts. When properly connected, a chain of stackable switches appears to the network administrator as a single switch and allows management of all switches and ports of the stack from a single management console. Operating a stack of switches as a single device not only allows a common configuration throughout, but it builds a single backplane between the switches. The shared backplane allows for both faster throughput between local switch ports and multiple uplink ports back to the aggregation layer of the enterprise network.

Unfortunately, nearly every networking vendor utilizes its own proprietary connectors, cables and software for its stackable switches, requiring a wiring closet full of the same product line of switches to take advantage of stacking.

Product differentiators among stackable switch vendors

While the stackable switch market is a mature and relatively stable one, each networking vendor adds its own unique features and functionality to separate itself from the pack. Unlike the revolutionary change seen in the data center switching market,  network edge vendors are evolving and innovating incrementally.

“Unlike other parts of the network, access layer stackable switches are a mature component. The little advances made in this space add up to significant improvements,” said Rohit Mehra, director of enterprise communications infrastructure for IDC.

Stackable switch vendors are paying particularly attention to power consumption and distribution. Many vendors are making their switches more green by minimizing power consumption. Cisco Systems, for example, offers the PowerStack solution for its stackable switches. With PowerStack, the switches within a stack treat the power supplies of each switch as a shared pool. A network administrator can allocate this shared pool PoE devices anywhere in the stack. The shared pool can also be used to power a switch in the stack whose own power supply has failed. The shared pool of power eliminates the need for secondary power supplies or dedicated power units.

Other vendors are extending the reach of the stack and enhancing the role of a stackable switch. SummitStack-V is a stacking solution from Extreme Networks that allows an enterprise to stack switches via 10 GbE ports that are up to 40 km apart from each other. This long distance stacking offers the backplane and administrative advantages of a stackable switch, even if the switches are nowhere near each other. Extreme also touts its latest stackable switch, the Summit X460 Series, as a versatile switch for use both at network edge and at the top of the server rack in the data center. While it remains to be seen if customers will embrace such a hybrid product for very disparate roles, the offering does highlight how many of the features required in the data center will trickle their way out to the network edge.

“With video, virtual desktop infrastructure and mobility solutions moving into enterprises, the wiring closet will require more bandwidth as well as greater intelligence and security at the network edge,” Mehra said.

Vendors position stackable switches for value

While networking vendors each offer features to differentiate themselves from the competition, nearly all vendors portray stackable switch gear as the value lines among their switching product lines. Most vendors have also brought some parity to their stackable switches and modular products by running both on a common operating system. A common software base eases configuration and management issues and allows organizations to standardize on policy and management throughout their enterprise network, from the data center core to the wiring closet edge.

This was first published in April 2011

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