Chapter 5 - Networking Devices

Question 1

a network interface card (NIC) is installed in your computer to connect, or interface, your computer to the network. It provides the physical, electrical, and electronic connections to the network media. The NIC is called a Layer 2 device because the information it uses for communication, the MAC address, resides on the Data Link layer.

Answer 1

NICs today usually have one, two, or more LEDs; one, usually green, is called a link light, indicating that an Ethernet connection has been established with the device on the other end of the cable, and it flickers when traffic is being passed back or forth. The other, or others, usually indicates the speed of the connection: 10, 100, or 1000 Mbps.

Question 2

The first LED you should verify is the link LED because if it’s not illuminated, the activity LED simply cannot illuminate.

Answer 2

There’s no universal standard for NIC LEDs, so check the manual to familiarize yourself with theones you are working with. But it’s not always that cut-and-dried that blinking LED can mean the NIC is receiving a proper signal from the hub or switch, but it can also indicate connectivity to and detection of a carrier on a segment.

Question 3

a hub is the device that connects all the segments of the network together in a star topology Ethernet network.

Answer 3

As a hub has no intelligence, it is a Layer 1 device. Each device in the network connects directly to the hub through a single cable and is used to connect multiple devices without segmenting a network.

Question 4

Most of the time, hubs really aren’t recommended for corporate networks because of their limitations.

Answer 4

It’s important to note that hubs are nothing more than glorified repeaters that are incapable of recognizing frames and data structures—the reason they act with such a lack of intelligence. A broadcast sent out by any device on the hub will be propagated to all devices connected to it. Hubs are not suggested for use in today’s corporate network for this reason.

Question 5

A bridge—specifically, a transparent bridge—is a network device that connects two similar network segments together.

Answer 5

A bridge—specifically, a transparent bridge—is a network device that connects two similar network segments together. Its primary function is to keep traffic separated on either side of the bridge, breaking up collision domains, as pictured in Figure 5.3.

Question 6

The main reasons you would place a bridge in your network would be to connect two segments together or to divide a busy network into two segments.

Answer 6

As bridges use MAC addresses to make forwarding decisions, they are considered Layer 2 devices.

Question 7

Bridges are software based, so, interestingly, you can think of a switch as a hardware-based, multiport bridge. In fact, the terms bridge and switch are often used interchangeably because the two devices used basically the same bridging technologies.

Answer 7

Switches connect multiple segments of a network together much like hubs do, but with three significant differences—a switch recognizes frames and pays attention to the source and destination MAC address of the incoming frame as well as the port on which it was received.

Question 8

A switch makes each of its ports a unique, singular collision domain. Hubs don’t do those things. They simply send anything they receive on one port out to all the others. As switches use MAC addresses to make forwarding decisions, they are considered Layer 2 devices.

Answer 8

So, if a switch determines that a frame’s final destination happens to be on a segment that’s connected via a different port than the one on which the frame was received, the switch will only forward the frame out from the specific port on which its destination is located.

Question 9

If the switch can’t figure out the location of the frame’s destination, it will flood the frame out every port except the one on which the frame port was received.

Answer 9

Switches that can perform the basic switching process and do not allow you to configure more advanced features—like adding an IP address for telnetting to the device or adding VLANs—are called unmanaged switches.

Question 10

Cisco switches that do allow an IP address to be configured for management with such applications as SNMP and do allow special ports to be configured (as in VoIP), are called managed switches.

Answer 10

Switches are Layer 2 devices, which means they segment the network with MAC addresses. If you see the term Layer 3 switch, that means you are talking about a router, not a Layer 2 switch. The terms router and Layer 3 switch are interchangeable.

Question 11

A router is a network device used to connect many, sometimes disparate, network segments together, combining them into what we call an internetwork.

Answer 11

As routers use IP addresses to make forwarding decisions, they are considered Layer 3 devices.

Question 12

Routers can have many different names: Layer 3 switch and multilayer switch are the most common, besides the name router, of course. Remember, if you hear just the word switch, that means a Layer 2 device. Routers, Layer 3 switches, and multilayer switches are all Layer 3 devices.

Answer 12

On a switch, you do not add an IP address since they only read to Layer 2, and most of the time, you never even need to configure a switch interface. First, they are enabled by default, and second, they are very good at auto-detecting the speed, duplex, and, in newer switches, even the Ethernet cable type (crossover or straight-through).

Question 13

A router is much different and an IP address is expected on each interface; they are not enabled by default, and a good Layer 3 network design must be considered before installing a router.

Answer 13

However, be aware that if your network interface card is set to half duplex and the switch port is configured for full duplex, the port will receive errors and you’ll eventually get a call from the user. This is why it is advised to just leave the defaults on your hosts and switch ports, but it is a troubleshooting spot to check when a problem is reported from a single user.

Question 14

Again, this is set to auto, but you may want to force the port to be 100 and full duplex. Typically, the NIC will run this without a problem and you’ll be sure you’re getting the most bang for your buck on your switch port.

Answer 14

A router interface will break up collisiondomains just as a switch interface does, but the purpose of a router interface is to create and maintain broadcast domains and connectivity of WAN services.

Question 15

Unlike switches, router interfaces do not just work when you plug them into the network—they must be configured and enabled. All ports are shut down by default,

Answer 15

Other types of IDSs are protocol based (PIDS), which monitor traffic for one protocol on one server, and application protocol based (APIDS), which monitor traffic for a group of servers running the same application (such as SQL). AP is just a hub that accepts wireless clients via an analog wireless signal. APs operate at Layer 2.

Question 16

The AP creates one collision domain and can only run half duplex, which is why you can describe an AP as being like a hub.

Answer 16

Both wired and wireless environments use a contention method to arbitrate access to the medium to help prevent collisions or at the least to recover from them when they occur.

Question 17

DHCP is an Application layer protocol. While the DORA components operate at Layer 2, the protocol is managed and responds to the Application layer. DHCP uses UDP ports 67 and 68.

Answer 17

IP address management (IPAM) tools are software products that integrate the management of DHCP and DNS. It is used to plan, track, and manage the IP addresses. With the integration of DNS ad DHCP each process is kept abreast of changes made to the other service.

Question 18

A multilayer switch (MLS) is a computer networking device that switches on Open Systems Interconnection (OSI) Layer 2 like an ordinary network switch but provides routing. A 24-port MLS gives you the best of both worlds. It operates at Layer 3 (routing) while still providing 24 collision domains, which a router could not do.

Answer 18

a load balancer can actually send incoming packets to multiple machines hidden behind one IP address—

Question 19

the fault tolerance, or redundancy, as well as the scalability so vital to large networking environments and e-commerce are some of the great benefits we gain using load balancers.

Answer 19

A Domain Name Service (DNS) server is one of the most important servers in your network and on the Internet as well. Why? Because without a DNS server, you would have to type http://206.123.114.186 instead of simply entering www.lammle.com.

Question 20

Microsoft’s Windows Internet Naming Service (WINS).

Answer 20

The following list includes some of the top-level domains currently in use:
.com A commercial organization. Most companies end up as part of this domain. .
.edu An educational establishment, or university
.gov A branch of the U.S. government.
.int An international organization, NATO or UN
.mil A branch of the U.S. military.
net A network organization.
.org A nonprofit organization.

Question 21

The .com domain is by far the largest, followed by the .edu domain.

Answer 21

a reverse lookup zone (or table) in the server and are used when an IP address is known but not a name.

Question 22

Third-Party/Cloud-Hosted DNS

Some smaller organizations find that it makes more sense to outsource the DNS function. Rather than hire and train staff to set up, configure, and maintain the infrastructure required to keep name resolution up and secure, they might find it more cost effective to utilize a third party who make it their business to provide this service.

Answer 22

A proxy server is basically a type of server that handles its client-machine requests by forwarding them on to other servers while allowing granular control over the traffic between the local LAN and the Internet.

Question 23

A proxy server operates at the Application layer.

Sometimes the proxy modifies the client’s request or a server’s response to it—or even handles the client’s request itself. It will actually cache, or “remember,” the specific server that would have normally been contacted for the request in case it’s needed another time. This behavior really speeds up the network’s function, thereby optimizing its performance.

Answer 23

have access to, which is a benefit for an administrator of the network if users are constantly connected to non-work sites and using all the WAN bandwidth.

Question 24

Web Proxy Server A web proxy server is usually used to create a web cache. You experience this when you Google a site The web proxy “remembers” you, and the site not only loads faster,

Answer 24

Web proxy
it sometimes even recalls your personal information by automatically filling in your username—or even your billing/shipping information when you place another order.

Question 25

Caching Proxy Server A caching proxy server speeds up the network’s service requests by recovering information from a client’s earlier request.

Answer 25

Packet shaping (also known as traffic shaping, it’s a form of rate limiting) is an Internetworking traffic management technique that delays some or all packets to bring them into compliance with your or your company’s traffic profile.

Question 26

Packet shaping

This process is used to optimize or guarantee performance, improve latency, and/or increase usable bandwidth for some kinds of packets by delaying other kinds, decided on by you.

Answer 26

Media converters are used when you need to convert from one type of cabling to another type. This might be required to convert from one type of fiber to another or from Ethernet to fiber, for example.

Media converters operate at Layer 1.

Question 27

Here’s a list of some of the nasty things that commonly cause LAN traffic congestion: Too many hosts in a broadcast domain Broadcast storms Multicasting Low bandwidth Adding hubs for connectivity to the network

Answer 27

The answer to fixing a huge but slow network is to break it up into a number of smaller networks—something called network segmentation. You do this by using devices like routers and switches, which are sometimes still referred to as bridges because switches still use bridging technologies.

Question 28

A switch can replace the hub, breaking up collision domains. Routers, by default, break up a broadcast domain.

Answer 28

And don’t forget that the router provides connections to WAN services as well. The router uses something called a serial interface for WAN connections: specifically, a V.35 physical interface.