CISCO NETWORKING ACADEMY PROGRAM CCNA 3 AND 4 COMPANION GUIDE PDF

To meet the many educational needs of the internetworking community, Cisco Systems established the Cisco Networking Academy Program. The Networking Academy is a comprehensive learning program that provides students with the Internet technolog[r]

Figure 3-37 Splicing of Different Types of Fiber
After the fiber-optic cable and connectors are installed, the connectors and the ends of the fibers must be kept spotlessly clean. The ends of the fibers should be covered with protective covers to prevent damage to the fiber ends.[r]

If the incident ray strikes the glass surface at exactly a 90-degree angle, the ray goes straight into the glass. The ray is not bent. But, if the angle of incidence is not exactly 90 degrees, then the ray that enters the glass (the transmitted ray) is bent. We call this bending of the entering r[r]

Each light source can be lighted and darkened quickly to send data 1s and 0s at a high number of bits per second.
Receiver
At the other end of the optical fiber from the transmitter is the receiver. It functions something like the photoelectric cell in a solar-powered calculator. W[r]

The Radio Wave/Microwave Spectrum
Computers send data signals electronically. Radio transmitters convert these electrical signals to radio waves. The radio waves are generated by changing electric currents in a transmitter’s antenna. These radio waves radiate out in straight lines from the antenn[r]

■ All band—All band interference affects the entire spectrum range. Bluetooth
technologies hop across the entire 2.4 GHz many times per second and can cause significant interference on an 802.11b network. It is not uncommon to see signs in facilities that use wireless networks requesting t[r]

Star and Extended-Star Topologies
The star topology , shown in Figure 2-42, is the most commonly used physical topology in Ethernet LANs. When installed, the star topology resembles spokes in a bicycle wheel. The star topology is made up of a central connection point that is a device such[r]

Like bridges, switches connect LAN segments, use a table of MAC addresses to deter- mine the segment on which a frame needs to be transmitted, and reduce traffic. Switches operate at much higher speeds than bridges.
Switches are data link layer devices that, like bridges, let multiple phy[r]

D. Too many nodes or not enough cable
22. Which of the following is true of a bridge and its forwarding decisions?
A. Bridges operate at OSI Layer 2 and use IP addresses to make decisions.
B. Bridges operate at OSI Layer 3 and use IP addresses to make decisions.

Figure 3-7 Screened Twisted-Pair Cable
However, shielded cable is more difficult to install than unshielded cable because the metallic shielding needs to be grounded. If improperly installed, STP and ScTP become very susceptible to noise problems because an ungrounded shield acts lik[r]

Layer 7: The Application Layer
The application layer is the OSI layer that is closest to the user. It provides network services to the user’s applications. It differs from the other layers in that it does not provide services to any other OSI layer; instead, it provides services only to applica-[r]

History and Evolution of Ethernet 253
802.3. The IEEE wanted to make sure that its standards were compatible with and fit into the ISO’s OSI reference model. The IEEE divides the OSI data link layer into two separate sublayers: Media Access Control (MAC) and Logical Link Con[r]

impedance A measurement of the resistance of the cable to AC and is measured in ohms.
insertion loss The combination of the effects of signal attenuation and impedance discontinuities on a communications link.
intelligent hub Sometimes called “smart hubs.” These devices basically f[r]

Figure 5-8 Ethernet II Frame Format
Table 5-3 lists the octet number and name for each Ethernet II frame field.
As indicated in Table 5-3, use of the Ethernet II Type field is incorporated into the cur- rent 802.3 frame definition. Upon receipt, a station must determine which h[r]

Figure 4-48 Modular Serial Port Interfaces
Routers and ISDN BRI Connections
With ISDN BRI, you can use two types of interfaces: BRI S/T and BRI U. In ISDN BRI service, a user (U) interface is the electrical interface for the twisted-pair wire connec- tion from a user to a[r]

Fluke Networks has coined the term ghost to mean energy (noise) detected on the cable that appears to be a frame but that lacks a valid SFD. To qualify as a ghost, this “frame” must be at least 72 octets long (including the preamble); otherwise, it is classified as a remote collision. Because of[r]

basically function as active hubs, but also include a microprocessor chip and diagnostic capabilities. They are more expensive than active hubs, but are useful in troubleshooting situations.
All devices that are attached to a hub hear all traffic. Therefore, hubs maintain a single collisio[r]

The TDR test is used not only to determine length, but also to identify the distance to wiring faults such as shorts and opens. When the pulse encounters an open, short, or poor connection, all or part of the pulse energy is reflected back to the tester, which can calculate the approximate[r]

The two most common wireless technologies used for networking are infrared (IR) and radio frequency (RF). IR technology has its weaknesses. Workstations and digital devices must be in the line of sight of the transmitter to operate. An IR-based network suits environments wher[r]

Each of the software components is stored in memory as a separate file. These files are also stored in different types of memory.
The Cisco IOS Software image is stored in a memory area called Flash. Flash memory provides nonvolatile storage of a Cisco IOS Software image that can be u[r]