Home > Articles

Networking Hardware

This chapter is from the book

Working with Network Connectivity Devices

Depending on the type of topology your network uses and the type of cabling you use (cabling is discussed in Chapter 4, "Building the Network Infrastructure"), your LAN might require some sort of connectivity device to connect the various network computers, printers, and other devices together. In cases where you need to extend your LAN (say, to the second floor of an office building) or add a large number of new users to the LAN, other connectivity devices might be required. Some of these connectivity devices merely serve to connect devices; others are used to boost the data signal traveling on the network medium, and still others actually participate in determining how data traffic should flow on the network.

Let's start our discussion of network connectivity devices with the hub, which is a device you would use on a small network, or even in a peer-to-peer networking situation, to connect computers. The other devices that we will look at, such as repeaters, switches, and routers, are often lumped under the blanket term internetworking devices. An internetwork is a network of LANs, meaning that some sort of connectivity technology is used to extend a LAN beyond its typical size or to connect different LANs together into one large network.

Hubs

Hubs are commonly used LAN connectivity devices (although inexpensive switches are rapidly replacing hubs on networks). They serve as the central connection points for LANs (hubs are used on LANs that embrace the star topology discussed in Chapter 2, "Different Needs, Different Networks"). A basic hub contains no active electronics and therefore cannot be used to extend a LAN (that is, extend it past the cabling distance specifications discussed in the next chapter). It basically organizes your cables and relays data signals to all the computers on the LAN.

Hubs are used on networks that use twisted-pair cabling. Ports available on the hub provide the connection points for the devices on the network. Computers and other devices are attached to the hub by individual network cables. Hubs come in many sizes and shapes and supply different numbers of ports.

In cases where the LAN outgrows the size of the hub, a new hub can be attached (the hubs are "daisy chained" together using a short connection cable often referred to as a rat tail) to the current hub, thus providing greater port density. Figure 3.5 shows a 24-port Ethernet hub.

Figure 3.5Figure 3.5 Hubs provide a connecting point for LAN nodes.

Hubs come in all sizes and shapes and are available in a wide range of prices. Typically, the more ports on the hub, the more expensive the hub. Hubs that support faster varieties of Ethernet, such as Fast Ethernet (which we discuss in the next chapter), will also cost more.

Repeaters

As you will find out in the next chapter, the different types of network cabling all have a maximum distance that they can move a data signal. In cases where a LAN must be extended beyond the maximum run for a particular cabling type, repeaters are used. A repeater takes the signal that it receives from computers and other devices on the LAN and regenerates the signal so that the signal maintains its integrity along a longer media run than is normally possible.

Repeaters don't have any capabilities for directing network traffic or deciding the particular route certain data should take; they are simple devices that just sit on the network, boosting the data signals they receive. The problem with repeaters is that they amplify the entire signal that they receive, including any line noise. So, in worst-case scenarios, they pass on data traffic that is barely discernable from the background noise on the line.

Bridges

A bridge is an internetworking device used to help conserve the bandwidth available on the network. When LANs really start to grow, network data traffic can begin to overwhelm the available bandwidth on network media.

One strategy for conserving network bandwidth is to chop the network up into smaller segments. These segments are connected to a bridge. Bridges are smarter than hubs and repeaters and actually use some software to help get the job done. A bridge is able to read the MAC address (also known as the hardware address—remember it's burned onto the NIC in each computer on the network) of each data packet circulating on the network segments connected to the bridge. By learning which MAC addresses live on each of the network segments, the bridge can help keep data traffic that is local to a particular segment from spreading to the other network segments that are serviced by the bridge.

Switches

A switch is another internetworking device used to manage the bandwidth on a large network. Switches are rapidly becoming one of the most used internetworking devices for connecting even smaller networks because they allow you some control over the use of the bandwidth on the network. A switch, which is often referred to as a "bridge on steroids," controls the flow of data by using the MAC address that is placed on each data packet (which coincides with the MAC address of a particular computer's network card). Switches divide networks into what are called Virtual LANs or VLANs. The great thing about a VLAN, which is a logical grouping of computers on the network into a sort of communication group, is that the computers don't have to be in close proximity or even on the same floor. This allows you to group computers that serve similar types of users into a VLAN. For example, even if your engineers are spread all over your company's office building, their computers can still be made part of the same VLAN, which would share bandwidth.

Switches use a combination of software and hardware to switch packets between computers and other devices on the network. Switches have their own operating system. Figure 3.6 shows the status of a VLAN (VLAN1) on a Cisco 2900 switch. Understanding what is being shown in this figure requires an understanding of the switch's OS. Basically, this particular screen shows the hardware/MAC address of the switch and the IP address of the switch. Other statistics relate to the number of packets sent and received by the switch (which are all at 0 because the switch has just been placed on the network).

Figure 3.6Figure 3.6 A proprietary switch operating system is used to configure and monitor a switch.

Because switches can offer a high density of connection ports, they can replace hubs on a network. This means that each computer on the network can be connected to its own port on the switch. When PCs are directly connected to a switch, the switch can supply each PC with a dedicated amount of bandwidth. For example, users on a 100Mbps Ethernet (fast Ethernet) network can realize bandwidth of 100Mbps. The computers don't compete for the bandwidth the way computers do on a network that is connected via a hub. This is why switches are rapidly replacing hubs. Inexpensive switches are even available for the small network and home network markets.

Some switch hardware can also take advantage of full-duplex access to the network media, which allows for the sending and receiving of data simultaneously on the network. This provides network access on an Ethernet network that would essentially be collision free (Ethernet networks experience data collisions pretty much as a rule; Ethernet is discussed in the next chapter). A computer on a Fast Ethernet network, which runs at 100Mbps, would actually realize a net total of 200Mbps throughput because sending and receiving can take place simultaneously on the full-duplex media.

Switches (because of the aforementioned reasons) are becoming very popular on both small and large networks. They have all but replaced bridges as the internetworking devices for conserving network bandwidth and expanding LANs into larger corporate internetworks. And they are also making the hub a thing of the past on smaller networks.

Routers

Routers are even smarter than bridges and switches (routers operate at the Network layer—a higher level in the OSI conceptual model than bridges and switches, which operate at the Data Link layer; we discuss all the layers of OSI in Chapter 5). A router uses a combination of hardware and software to actually "route" data from its source to its destination. (By software, I mean an operating system.) Routers actually have a very sophisticated OS that allows you to configure their various connection ports. You can set up a router to route data packets from a number of different network protocol stacks, including TCP/IP, IPX/SPX, and AppleTalk (protocols are discussed in Chapter 4).

Routers are used to segment LANs that have become very large and congested with data traffic. Routers are also used to connect remote LANs together using different WAN technologies.

Figure 3.7 shows a Cisco 2516 router. This router has a built-in hub and three different WAN connection points. Notice the BRI port marked in the figure. BRI stands for ISDN Basic Rate Interface, which allows this router to connect to a remote network using an ISDN connection (ISDN and other WAN technologies are discussed in Chapter 13, "Expanding a LAN with WAN Technology").

Routers divide large networks into logical segments called subnets. This division of the network is based on the addressing scheme the network uses, such as IP addresses. Data traffic related to a particular subnet is kept local. The router only forwards data that is meant for other subnets on the extended network. This routing of network data helps conserve network bandwidth.

Figure 3.7Figure 3.7 Routers are used to segment networks into logical subsets.

Routers decide how to forward data packets to their destinations based on a routing table. Routers use protocols built in to their operating system to identify neighboring routers and their network addresses (such as IP addresses). This allows routers to build a routing table. Figure 3.8 shows the command-line interface used on a Cisco router. This figure also shows the IP routing table for a small network that consists of two connected Cisco routers. Each of the subnets shown at the bottom of the table (notice the list of IP addresses) represents a different router interface. 10.2.0.0 and 10.3.0.0 are on the router that supplied this screen. The subnets 10.1.0.0 and 132.1.0.0 were discovered by the router (using the RIP protocol) on a connected router.

Figure 3.8Figure 3.8 Routers build and use a routing table to determine where data packets should be forwarded.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020