Cisco Certification Exams & Training Materials

Testking CCNP 642-825

Implementing Secure Converged Wide Area Networks

Exam Number: 642-825
Associated Certifications: CCNP
Duration: 90 minutes
Available Languages: English
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QUESTION 1:

A few small Certkiller locations use HFC cable to connect to the Certkiller WAN. Which HFC cable network statement is true about the downstream data channel to the customer and the upstream data channel to the service provider?

A. The upstream data path is assigned a channel in a higher frequency range than the downstream path has.
B. The downstream data path is assigned a 30 MHz channel and the upstream data path is assigned a 1 MHz channel.
C. The downstream data path is assigned a fixed bandwidth channel and the upstream data path uses a variable bandwidth channel.
D. Both upstream and downstream data paths are assigned in 6 MHz channels.
E. None of the above. Answer: D
Explanation:
Hybrid fiber-coaxial (HFC): A mixed optical-coaxial network in which optical fiber replaces some or all of the traditional trunk portion of the cable network.
The HFC architecture is the evolution of an initial cable system and signifies a network that incorporates both optical fiber along with coaxial cable to create a broadband network. By upgrading a cable plant to an HFC architecture, you can deploy a data network over an HFC system to offer high-speed Internet services and you can serve
more subscribers. The cable network is segmented into smaller service areas in which fewer amplifiers are cascaded after each optical node-typically five or fewer. The
tree-and-branch network architecture for HFC can be a fiber backbone, cable area network, superdistribution, fiber to the feeder, or a ring.
Downstream: An RF signal transmission (TV channels, data) from source (headend) to the destination (subscribers). Downstream is also called a forward path.
Upstream: An RF signal transmission opposite to downstream-from subscribers to the headend. Upstream is also called a return or reverse path.
Delivering services over a cable network requires different RF frequencies-the outgoing frequencies are in the 50-to-860 MHz range, the incoming are in the 5-to-42 MHz range.
To deliver data services over a cable network TV channels which usually operate at 6
MHz range for the downstream, and 6 MHz or less (for asymmetric cable connections)
for upstream traffic from the corresponding frequency range are usually used.

QUESTION 2:

Many small Certkiller branch offices use broadband cable for data connection access. Which three modulation signaling standards are used in broadband cable technology? (Select three)

A. S-Video

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B. NTSC
C. SECAM D. PAL
E. FEC F. FDM G. MLP
Answer: B, C, D Explanation:
Broadband: Data transmission where multiple pieces of data are sent simultaneously to increase the effective rate of transmission. In cable systems, the term broadband refers to the frequency-division multiplexing (FDM) of many signals in a wide radio frequency
(RF) bandwidth over an HFC network, and the capability to handle vast amounts of information.
NTSC is a North American TV technical standard for analog TV systems. The standard was created in 1941 and is named after the National Television System Committee
formed in 1940. The standard uses a 6-MHz modulated signal. PAL is a color encoding system used in broadcast television systems in most of Europe, Asia, Africa, Australia, Brazil, and Argentina, and uses a 6-MHz, 7-MHz, or 8-MHz modulated signal. The color difference signals an alternate phase at the horizontal line rate. SECAM is an analog
color TV system used in France and certain Eastern European countries that uses an
8-MHz modulated signal.

QUESTION 3:

Some of the smaller Certkiller locations use HFC cable to connect to the Certkiller
WAN. Which two statements are true about broadband cable (HFC) systems?
(Select two)

A. Cable modems operate at Layers 1, 2, and 3 of the OSI model. B. Cable modems operate at Layers 1 and 2 of the OSI model.
C. A function of the cable modem termination system is to convert the digital data stream from the end user host into a modulated RF signal for transmission onto the cable system.
D. Cable modems only operate at Layer 1 of the OSI model.
E. A function of the cable modem termination system (CMTS) is to convert the modulated signal from the cable modem into a digital signal.
Answer: B, E Explanation:
Hybrid fiber-coaxial (HFC): A mixed optical-coaxial network in which optical fiber replaces some or all of the traditional trunk portion of the cable network.
The HFC architecture is the evolution of an initial cable system and signifies a network that incorporates both optical fiber along with coaxial cable to create a broadband network. By upgrading a cable plant to an HFC architecture, you can deploy a data

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network over an HFC system to offer high-speed Internet services and you can serve
more subscribers. The cable network is segmented into smaller service areas in which fewer amplifiers are cascaded after each optical node-typically five or fewer. The
tree-and-branch network architecture for HFC can be a fiber backbone, cable area network, superdistribution, fiber to the feeder, or a ring.

QUESTION 4:

A Certkiller remote user is getting Internet access from the local cable provider. When an individual is connected to the Internet by way of a CATV cable service, what kind of traffic is considered upstream traffic?

A. Traffic going from the user’s home traveling to the headend. B. Broadcast traffic, including the cable TV signals.
C. Traffic between the headend and the TV signal.
D. Traffic between the headend and the supplier antenna.
E. Traffic from outside the local cable segment serving the user’s home. F. All of the above can be considered upstream
Answer: A Explanation:
In the CATV space, the downstream channels in a cable plant (cable head-end to subscribers) is a point-to-multipoint channel. This does have very similar characteristics
to transmitting over an Ethernet segment where one transmitter is being listened to by
many receivers. The major difference is that base-band modulation has been replaced by
a more densely modulated RF carrier with very sophisticated adaptive signal processing and forward error correction (FEC).
In the upstream direction (subscriber cable modems transmitting towards the head-end)
the environment is many transmitters and one receiver. This introduces the need for
precise scheduling of packet transmissions to achieve high utilization and precise power control so as to not overdrive the receiver or other amplifier electronics in the cable system. Since the upstream direction is like a single receiver with many antennas, the channels are much more susceptible to interfering noise products. In the cable industry,
we generally call this ingress noise. As ingress noise is an inherent part of CATV plants, the observable impact is an unfortunate rise in the average noise floor in the upstream channel. To overcome this noise jungle, upstream modulation is not as dense as in the downstream and we have to use more effective FEC as used in the downstream.
Reference: http://www.cisco.com/warp/public/759/ipj_1-3/ipj_1-3_catv.html

QUESTION 5:

A new cable modem was shipped to the home of a Certkiller user, where it is being installed for the first time. When a DOCSIS 1.1 compliant cable modem first initializes, (boots up) what does it do?

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A. Establishes IP connectivity (DHCP).
B. Determines the time of day.
C. Requests a DOCSIS configuration file from a TFTP server.
D. Scan for a downstream channel and the establishment of timing synchronization with the CMTS.
E. None of the above. Answer: D
Explanation:
According to the DOCSIS (Data-over-Cable Service Interface Specifications) when you first power up a cable modem it starts scanning (starting at a low frequency) for a cable signal. When it ‘hears’ a cable modem stream it listens for a broadcast (from the service provider) which contains information (ie. frequency) needed to talk back with the head end. It then ‘talks back’ and if it communicates the right authentication information, it is allowed to proceed.
References: Page 225 of the CCNP Self-Study BCRAN (642-821) ISBN: 1-58720-084-8
http://www.cisco.com/en/US/products/hw/cable/ps2217/products_feature_guide_chapter09186a008019b57f.ht
m

QUESTION 6:

You are building a small network at your home and you intend on connecting your cable modem to a Cisco router. Which router interface would you connect the modem to?

A. Synchronous serial B. Asynchronous serial C. Ethernet
D. auxiliary
E. BRI Answer: C
Explanation:
In certain environments where a non Cisco Cable Modem (CM) is used, and the CM is only capable of bridging, a Cisco router such as the Cisco 806 can be connected to the
Cable Modem via the Ethernet interface. The routing can then be performed by the Cisco router behind the Cable Modem and the Client PC or Customer Premises Equipment
(CPE) will be connected to the Cisco router. Network Address Translation (NAT) can then be configured on the Cisco router.
When the Cisco router is connected behind the Cable Modem the first problem that might
be encountered is not obtaining an IP address dynamically on the Cisco router’s Ethernet interface. Most Internet Service Providers (ISPs) allow only one host or PC behind the Cable Modem. Some ISPs assign an IP address to the PC based on the host name. Therefore, if you have a Cisco router behind the Cable Modem, then the host name for

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