Actualtests CCNP 642-825
642-825 : Implementing Secure Converged Wide Area Networks Last Updated Thursday, September 25, 2008 with 287 Questions
ISCW - Implementing Secure Converged Wide Area Networks
Exam Number: 642-825 Exam
Associated Certifications: ISCW - Implementing Secure Converged Wide Area Networks
Duration: 310 Q&As
Available Language(s): English
Exam Details
The Implementing Secure Converged Wide Area Networks (ISCW 642-825) is a qualifying exam for the Cisco Certified Network Professional CCNP®. The ISCW 642-825 exam will certify that the successful candidate has important knowledge and skills necessary to secure and expand the reach of an enterprise network to teleworkers and remote sites with focus on securing remote access and VPN client configuration. The exam covers topics on Cisco hierarchical network model as it pertains to the WAN, teleworker configuration and access, frame mode MPLS, site-to-site IPSEC VPN, Cisco EZVPN, strategies used to mitigate network attacks, Cisco device hardening and IOS firewall features.
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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)
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A. S-Video
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.
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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.
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:
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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?
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
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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
the router configured using the hostname command should be the same host name given
by the ISP.
Example:
QUESTION 7:
When a cable modem is being provisioned to operate with a host system for Internet
services, which two options must occur before Layer 1 and 2 connectivity can
occur? (Choose two)
A. The cable modem must request an IP address and core configuration information from
a Dynamic Host Configuration Protocol (DHCP) server.
B. The cable modem powering up must scan and lock on the RF data channel in the
downstream path.
C. The modem must request a DOCSIS configuration file from a TFTP server.
D. The cable modem must register with the CMTS.
E. The modem must read specific maintenance messages in the downstream path.
Answer: B, E
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. Once these steps are completed, layers 1 and 2 will be operational.
QUESTION 8:
How is cable broadband technology able to transmit downstream and upstream
data while at the same time delivering television content?
A. The cable operator uses the VHF hyperband to transmit and receive data signals.
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B. The cable operator assigns any available spectrum to data, depending on how its own
television spectrum is being used.
C. The cable operator uses specific bandwidths for data signals specified by DOCSIS.
D. The cable operator places its data signals into clean areas where there is no
interference from noise or other signals.
Answer: C
Explanation:
Developed by CableLabs and approved by the ITU in March 1998, Data Over
Cable Service Interface Specification (DOCSIS) defines interface standards for
cable modems and supporting equipment. In a cable TV system, signals from the
various channels are each given a 6-MHz slice of the cable’s available bandwidth and
then sent down the cable to your house. In some systems, coaxial cable is the only
medium used for distributing signals.
When a cable company offers Internet access over the cable, Internet information can use
the same cables because the cable modem system puts downstream data — data sent from
the Internet to an individual computer — into a 6-MHz channel. On the cable, the data
looks just like a TV channel. So Internet downstream data takes up the same amount of
cable space as any single channel of programming. Upstream data — information sent
from an individual back to the Internet — requires even less of the cable’s bandwidth, just
2 MHz, since the assumption is that most people download far more information than
they upload.
QUESTION 9:
Certkiller operates a DSL network. What does the “dsl operating-mode auto”
command configure on a Cisco router?
A. It configures a Cisco router to automatically detect the proper modulation method to
use when connecting an ATM interface.
B. It configures a Cisco router to automatically detect the proper DSL type (ADSL,
IDSL, HDSL, VDSL) to use when connecting an ATM interface.
C. It configures a Cisco router to automatically detect the proper encapsulation method to
use when connecting an ATM interface.
D. It configures a Cisco router to automatically detect the proper authentication method
to use when connecting an ATM interface.
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E. None of the above
Answer: A
Explanation:
dsloperating-mode auto interface configuration command to specify that the router
automatically detect the DSL modulation that the service provider is using and set the
DSL modulation to match. An incompatible DSL modulation configuration can result in
failure to establish a DSL connection to the DSLAM of the service provider
Example:
QUESTION 10:
Certkiller is a DSL service provider using providing xDSL to its customers. Which
statement about xDSL implementations is true?
A. All xDSL standards operate in lower frequencies than the POTS system and can
therefore coexist on the same media.
B. Other than providing higher data rates, HDSL is identical to ADSL.
C. The ADSL standard operates in higher frequencies than the POTS system and can
therefore coexist on the same media.
D. The HDSL standard operates in higher frequencies than the POTS system and can
therefore coexist on the same media.
E. All xDSL standards operate in higher frequencies than the POTS system and therefore
can coexist on the same media.
F. None of the above.
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