Top Tips for Buying Used Network Switches on eBay

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Top Tips for Buying Used Network Switches on eBay

A network is defined as a collection of devices sharing resources. Of course, business networks can encompass thousands of users. As the number of devices per person continues to grow, even the number of home network users is increasing. Regulating the traffic between these devices is the job of a network switch. When a hub is used in this role, it allows the free transmission of information packets from one user to the entire network. A network switch, however, uses "intelligent" filtering, in that it reads each message before directing it only to the intended target.

Implementing a network switch can improve both capacity and speed in the network, which, in turn, increases productivity. However, network switches are not meant for every network. Therefore, it pays to understand their functionality and compare that against a home or office network. Once a basic understanding is obtained, buyers are primed to visit eBay and find the used network switches they are looking for.

Network Congestion

Just as too many cars on a given motorway slows down movement, so too does the presence of many users on a single network slow down transmissions. The reason for this is the increased competition for Ethernet lines. For example, if a 10 Mbps Ethernet network switch processes a moderate load, it delivers 35 per cent utilisation. Once packet overhead, collisions, and inter-packet gaps are factored into the mix, the capacity drops to 2.5 Mbps. When the same load is processed via a Fast Ethernet or Gigabit Ethernet, the numbers jump to 25 Mbps or 250 Mbps of real data. Back to the automobile analogy, the greater the traffic on the Ethernet, the higher the frequency of collision.

Because Ethernet is a shared media, information transmitted through its cables is prone to colliding in transit. With the use of a network switch, however, the incoming and outgoing data packets have their own paths. In eliminating the risk of collision and the resultant need for message retransmission, network administrators ensure a faster connection speed.

Measuring Network Efficiency

It is important for technology administrators to be able to assess their network's efficiency. To do so, there are four things to measure: the amount of traffic, the size of the information packets, the number of nodes, and the diameter of the network. Once these factors have been identified, they can measure the efficiency of the network by ascertaining both collision and utilisation rates, as well as the deviation between average and peak loads.

Getting a general picture of the network's health is its utilisation rate, as rates over 35 per cent, the optimum utilisation, may raise concern. Ultimately, a network switch found to be operating at "wire speed" when it processes minimum information packet sizes at full Ethernet speed. Full wire speeds of Ethernet and Fast Ethernet are 14,480 packets per second (pps) and 148,800 pps, respectively.

Why Network Switches Are Winning the Battle over Hubs

As previously discussed, network switches are higher in cost than their hub counterparts. Still, their use is consistently rising, with each year nearly double the switches sold from the last. Beyond the hub being an older technology, the price gap between the two is lessening. Another factor for the change is that network switches provide added functionality and faster processing speed with the same simple plug-and-play installation.

The use of a switch in network design serves to divide a single, large network into smaller, more manageable ones, thus reducing distance and removing repeater limitations. Also, in dividing information packet transfers, a network switch relieves congestion by reducing collisions. While the impact of less congestion is not as easily measured as that of reduced distance, it is nonetheless the biggest determinant in network performance and productivity. Add to this the fact that, due to its analysis and redirection of each information packet, any switch can cause slight delays in transmission. Therefore, it pays to measure the benefits of network switches against the network at hand.

The first step is to analyse the collision rates and utilisation of the hub currently in place. In general, a collision rate in excess of 10 per cent, or utilisation of over 35 per cent, warrants a closer look. Bear in mind that, the greater the number of devices connected to the network, the more taxed it is. This often translates into more frequent collisions and delayed communication due to the need for retransmission. If there are no issues with congestion or productivity, there is no need to change the set-up.

Replacing or Adding Network Switches

In shared networks that are relatively full, it is a good idea to replace a central hub with a switch. Doing so isolates each segment's relevant traffic, which in turn, delivers a faster network connection to all linked devices. Often though, with this growth in users and performance come new bottlenecks. When this occurs, it is time to consider adding additional switched ports. The addition of Ethernet, Fast Ethernet, or Gigabit Ethernet switch ports serves to improve performance.

How to Select the Right Network Switch

Whether the system administrator is looking at purchasing a new or used network switch, performing a review of switch terminology and functionality is a necessary first step. Amongst the terms and features with which to familiarise oneself are the following: number of users, network infrastructure, network needs, and the role of the switch.

Number of Users

The need for additional ports increases along with the number of users connected to the network. However, more is not always better, or needed, as prices increase as ports do. For this reason, an accurate evaluation of needs, both present and near future, should be performed prior to selecting port proliferation. Obtaining a switch with 12 ports, for example, is sufficient with 10 or fewer users; not only does this well satisfy current needs, but it allows for moderate growth in the next couple of years.

Network Infrastructure

A good rule of thumb is to buy one network switch for every 50 networked devices. It follows, then, that additional switches may be necessary the faster the number of users grows.

Network Needs

An exception to the rule for determining network switch quantity based on number of users is the how they plan to use the network. General business correspondence, Internet use, and accessibility would probably be fine with a switch utilising standard Ethernet; however, as more files are transferred or the need for super-fast connections grows, the Ethernet capacity may need to be adjusted upward. While a network switch with a 100-megabit port should suffice for basic needs, greater capacity may necessitate Fast Ethernet or Gigabit Ethernet functionality.

Role of the Switch

Think of a network switch as the command centre for all networked devices. In general, larger networks see just one of the switches serving as the core. With its increased importance and greater responsibility, the core network switch should have noticeably more power than others on the network. When seeking core switches, buyers are advised to look no lower than a gigabit. Of course, an access switch can be substituted for the core network switch. Although this option is less expensive, it also correlates with slower network operation.

Additional Features

Although buyers may have identified a network switch that has the basics covered, they may want to take a moment and explore additional features to improve the functionality of larger networks. Another good reason to perform this extra analysis now is to avoid the costly need of replacing network switches before their time. Amongst the features that bear consideration are configuration interface access, layer capability, and the choice between managed and unmanaged networks.

Calculate the Price

While the tendency to obtain the best bargain is a strong one, forsaking necessary functionality in the name of lower prices is not always a wise decision, especially when shopping for larger networks. Another thing that bears remembering is that the same features may cost more or less, depending on the brand.

Of course, shopping eBay for used network switches automatically provides cost savings over buying new. In obtaining a pre-owned model, buyers can almost always increase the functionality of their new network switch without spending the extra money.

Top Tips for Buying Used Network Switches on eBay

Buying a used network switch is much the same as hunting for a new one, except with savings built in. The trick is to match existing needs with switch capacities to ensure a rewarding, and functional, purchase. In reviewing product options, it is important to consider the following factors: backplane bandwidth, Ethernet channel, port count, Power over Ethernet (PoE), Quality of Service (QoS), remote administration, routing or firewall features, and stackability.

Features

Functionality

Backplane Bandwidth

Higher backplane bandwidth allows for a greater number of simultaneous conversations; general rule of thumb is to look for 10 times the backplane bandwidth for Ethernet capacity

Ethernet Channel, Bonding, and Link aggregation

This capacity enables merging multiple ports into a single trunk

Port Count

Need for additional ports increases based on number of users; individual port link speed is a consideration too

Power over Ethernet (PoE)

Flexibility and convenience intersect when the Ethernet cable also provides electrical power; devices may be installed even if electrical outlets are nowhere near

Quality of Service (QoS)

Enables the transport of information with special requirements; essential when VoIP is involved

Remote Administration

Allows for the configuration and monitoring of HTTP, proprietary tools, switch, and telnet, amongst others, without the need for onsite administration

Routing or Firewall Features

When looking for advanced network switches, routing functionality is essential

Stackability

As network access needs grow, the presence of a stackable network switch enables the addition of extra switches, in lieu of replacing the entire switch

Consideration of these features is especially important when managing a large network of users. Having fewer devices, such as in a home network environment, may eliminate the need for much of the above features.

How to Buy a Used Network Switch on eBay

Armed with a thorough analysis of your network needs, including number of users, frequency of communication, and file transfer size, you have moved on to evaluate network switches and their capabilities. Amongst other things, you have identified your system's requirements in terms of port count, PoE, QoS, stackability, and backplane bandwidth. You also know you can strengthen your budget further by shopping for reliable used network switches rather than new ones. Directing your browser to eBay, you are ready to view the site's extensive inventory of used network switches.

eBay allows you to search by almost any relevant term. Some common search criteria for used network switches may include Ethernet capacity, such as 100 Mbps or 1000 Mbps; manufacturers, such as NETGEAR and Linksys; or PoE functionality. eBay displays search results in terms of relevancy, taking into consideration the title and description of each product. Be sure to review item descriptions before committing to a purchase.

Conclusion

Computer use is all about speed. Everyone wants the fastest processor, the fastest Internet surfing, the fastest file transfer, and much more. When a network involves multiple users, the shortcomings of a hub become apparent, especially in relation to data transmission. Whereas a hub acts as a broadcast centre, receiving messages and disseminating them to the wide audience, a network switch is more like a train station: Messages arrive, but rather than distributing them to all locations, the switch takes note of their individual destinations and directs them independently.

Network switches can be evaluated by number of ports, expansion capacity via combination, or Ethernet speed, including Fast (100 Mbps) and Gigabit (1000 Mbps). While the cost in network switches can vary greatly depending not only on features and speed, but also manufacturer, buyers seeking the best deal often turn to eBay and shop used network switches. Seller satisfaction ratings, reliable return policies, and technological proficiency help ensure buyers find used network switches to meet their needs.

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