Cisco 642-825 Free Demo – 4
Posted on | January 29, 2010 | No Comments
Q17
When designing an ADSL network; if you want minimal local loop impairments, what should be the maximum distance of your lines?
A. 1000 feet (0.3 km)
B. 4000 feet (1,5 km)
C. 12,000 feet (3.65 km)
D. 18,000 feet (5,5 km)
E. 28,000 feet (8.52 km)
Answer: D
Explanation:
DSL is a highly distance-sensitive technology. As the distance from the CO increases, the signal quality and connection speeds decrease. ADSL service is limited to a maximum distance of 18,000 feet (5460 m) between the DSL CPE and the DSLAM, although many ADSL providers place an even lower limit on the distance to ensure quality. The 18,000-foot distance limitation for DSL is not a limitation for voice telephone calls, but for data transmission. The telco uses small amplifiers, called loading coils, to boost voice signals. Loading coils have a nasty tendency to disrupt DSL data signals. This means that if there are loading coils in the loop between the CPE and CO, you probably are not within an area that can receive DSL service.
Reference:
Cisco Press – BCRAN 821 – Exam Certification Guide 2004 (ISBN 1-587208) Page 247
Q18
A new ADSL line is being installed in the home office of the Exambible administrator.
What best describes ADSL?
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A. Equal upload and downloads speeds.
B. Slow upload, fast download speeds.
C. An ISDN line with no D channel.
D. Used as a T-1 replacement.
Answer: B
Explanation:
The variation called ADSL (Asymmetric Digital Subscriber Line) is the form of DSL that will become most familiar to home and small business users. ADSL is called “asymmetric” because most of its two-way or duplex bandwidth is devoted to the downstream direction, sending data to the user. Only a small portion of bandwidth is available for upstream or user-interaction messages. However, most Internet and especially graphics- or multi-media intensive Web data need lots of downstream bandwidth, but user requests and responses are small and require little upstream bandwidth. Using ADSL, up to 6.1 megabits per second of data can be sent downstream and up to 640 Kbps upstream. The high downstream bandwidth means that your telephone line will be able to bring motion video, audio, and 3-D images to your computer or hooked-in TV set. In addition, a small portion of the downstream bandwidth can be devoted to voice rather data, and you can hold phone conversations without requiring a separate line.
Reference:
http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci213915,00.html
Q19
Which two statements are true about DSL? (Choose two)
A. SDSL and POTS can work together.
B. It uses the unused bandwidth of your existing phone line.
C. Bandwidth is shared among users in the same geographical area.
D. It has a maximum distance limitation of 18,000 feet from the CO.
Answer: B, D
Explanation:
DSL is a very high-speed connection that uses the same wires as a regular telephone line.
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Precisely how much benefit you see will greatly depend on how far you are from the central office of the company providing the ADSL service. ADSL is a distance-sensitive technology: As the connection’s length increases, the signal quality decreases and the connection speed goes down. The limit for ADSL service is 18,000 feet (5,460 meters) from the central office, though for speed and quality of service reasons many ADSL providers place a lower limit on the distances for the service. At the extremes of the distance limits, ADSL customers may see speeds far below the promised maximums, while customers nearer the central office have faster connections and may see extremely high speeds in the future. ADSL technology can provide maximum downstream (Internet to customer) speeds of up to 8 megabits per second (Mbps) at a distance of about 6,000 feet (1,820 meters), and upstream speeds of up to 640 kilobits per second (Kbps). In practice, the best speeds widely offered today are 1.5 Mbps downstream, with upstream speeds varying between 64 and 640 Kbps.
Section 3: Configure ADSL (i.e., PPPoE or PPPoA) (11
Questions)
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Q20
Two Exambible routers are connected as shown below:
Exambible 1 is configured as shown below:
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Refer to the exhibit and the partial configuration on the Exambible router.
The Exambible DSL Router is connected to a service provider using a PPPoE session over a DSL line. The FTP traffic, generated from inside the network 10.92.1.0/24, fails to reach the PPPoE Server. What should be configured on the DSL Router to fix the problem?
A. The ip mtu command with a bytes argument set greater than 1500 needs to be configured for the Dialer1 interface.
B. The ip mtu command with a bytes argument set lower than 1500 needs to be configured for the ATM0 interface.
C. The ip mtu command with a bytes argument set greater than 1500 needs to be configured for the ATM0 interface.
D. The ip mtu command with a bytes argument set lower than 1500 needs to be configured for the Dialer1 interface.
E. None of the above
Answer: D
Refecener: 642-825
More Cisco Exam Links: 642-901 642-825 640-816 000-081
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