Cisco Certified Network Associate
Questions, Answers, Braindumps (640-802)
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Question : 1
When files are transferred between a host and an FTP
server, the data is divided into smaller pieces for
transmission. As these pieces arrive at the destination
host, they must be reassembled to reconstruct the original
file. What provides for the reassembly of these pieces
into the correct order?
A. The sequence number in the TCP header
B. The Start Frame Delimiter in the 802.3 Preamble
C. The TTL in the IP header
D. The acknowledgement number in the segment header
E. The frame check sequence in the Ethernet frame trailer
The Transport layer can provide reliable networking
via acknowledgments, sequencing, and flow control.
Acknowledgments Delivered segments are acknowledged
to the sender. If they are not acknowledged, the sender
Sequencing Data segments are sequenced into their original
order when they arrive at the destination.
Flow Control Provides buffer controls that prevent packet
flooding to the destination host. Buffers store bursts
of data for processing when the transmission is complete.
Layer 4 protocols include the following:
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)
Sequenced Packet Exchange (SPX)A reliable communications
protocol created by Novell NetWare
Question : 2
You have just installed a new web server on the Abc
network. You are required to ensure that the web server
is accessible from the Internet. The network uses private
addressing, so an IP-to-registered address mapping is
required. To do this, you enter the following command:
You unsuccessfully try to ping the Internet from a PC
host on the LAN. During the troubleshooting process,
you enter the "show ip nat translations" command
but the output is blank. What is the most likely cause
of the problem?
A. The keyword overload is missing from the command.
B. The NAT pool must be defined first.
C. An access list must be defined to create static NAT
D. The interfaces must be configured for NAT.
E. None of the above
In order to successfully configure a static NAT translation,
the interfaces must be configured for NAT, in addition
to the global NAT command that was entered. The router
interface that lies on the inside part of the network
must be defined using the "ip nat inside"
command. Similarly, the WAN interface that is being
used for the Internet connection must be defined using
the "ip nat outside" command.
A. In order to make an internal server reachable from
the Internet, a static one to one NAT entry must be
configured for the server. The keyword "overload"
is used to configure many to one NAT, or PAT.
B, C. This need not be done in order to create a static
NAT entry. These steps are typically done in setting
up NAT so that inside LAN users can access the Internet
Question : 3
Which protocol below uses TCP port 443 at layer 4?
F. None of the above
HTTPS is the secured version of the HTTP application,
which normally uses 128 bit SSL encryption to secure
the information sent and received on a web page. An
example is a banking web site, or a trustworthy shopping
web site that takes credit card information. It is an
application layer protocol which uses TCP port 443.
A. HTML is not a protocol.
C. TFTP uses UDP port 69.
D. Telnet uses TCP port 23.
E. SMTP uses TCP port 25.
Question : 4
As a CCNA candidate, you will be expected to know the
OSI model very well. Which of the following are associated
with the application layer (layer 7) of the OSI model?
Answer: B, C
The application layer is the top layer of the OSI model
and is used to describe the end user applications that
can be used over a network.
Layer Name Examples
Application (layer 7) Telnet, HTTP, FTP, WWW browsers,
NFS, SMTP gateways, SNMP
A. TCP resides at layer 4.
D. ARP is a function of the data link layer, which is
E. IP is used at layer 3 (network layer).
CCNA Self-Study CCNA INTRO exam certification Guide
(Cisco Press, ISBN 1-58720-094-5) Page 34.
Question : 5
As the Abc network administrator, you are required to
have a firm understanding of the OSI model. Why does
the data communication industry use the layered OSI
reference model? (Choose two)
A. It enables equipment from different vendors to use
the same electronic components, thus saving research
and development funds
B. It encourages industry standardization by defining
what functions occur at each layer of the model
C. It divides the network communication process into
smaller and simpler components; thus aiding component
development, design and troubleshooting
D. It provides a means by which changes in functionality
in one layer require changes in other layers
E. It supports the evolution of multiple competing standards
and thus provides business opportunities for equipment
Answer: B, C
The OSI (Open System Interconnection) reference model
was created as a reference point for communications
devices. A layered approach is used to segment the entire
telecommunications process into a series of smaller
A is correct because it encourages a level of standardization
by encouraging that functions be compared to known layers.
D is also correct because it allows engineers to focus
on the development, refining, and perfection of simpler
Question : 6
You need to describe the various types of flow control
to your co-workers. Which of the following are types
of flow control that can be used in a network? (Choose
A. Congestion avoidance
E. Load Balacing
F. Fast Forward
Answer: A, B, D
Question : 7
Which of the protocols below use TCP at the transport
layer? (Select four)
Answer: B, D, E, F.
SMTP (Simple Mail Transfer Profile for email), FTP (File
Transfer Protocol), and HTTP/HTTPS (Hyper Text Transfer
Protocol for internet) all use TCP because of the reliable
delivery mechanism. SMTP uses TCP port 25, FTP uses
TCP ports 20 and 21, HTTP uses TCP port 80, and HTTPS
uses TCP port 443.
A, C: SNMP and TFTP use UDP as the transport mechanism.
Generally speaking, protocols that use the keywords
"trivial" or "simple" uses UDP,
since connectionless, best effort delivery mechanism
CCNA Self-Study CCNA INTRO exam certification Guide
(Cisco Press, ISBN 1-58720-094-5) Page 163.
Question : 8
Acknowledgements, sequencing, and flow control are functions
that are handled by which layer of the OSI model?
A. Layer 5
B. Layer 4
C. Layer 7
D. Layer 6
E. Layer 3
F. Layer 2
G. Layer 1
Question : 9
A receiving host has failed to receive all of the segments
that it should acknowledge. What can the host do to
improve the reliability of this communication session?
A. Start a new session using UDP
B. Obtain a new IP address from the DHCP server
C. Use a different source port for the session
D. Decrease the sequence number
E. Decrease the window size
A TCP window the amount of outstanding (unacknowledged
by the recipient) data a sender can send on a particular
connection before it gets an acknowledgment back from
the receiver that it has gotten some of it.
For example if a pair of hosts are talking over a TCP
connection that has a TCP window size of 64 KB (kilobytes),
the sender can only send 64 KB of data and then it must
stop and wait for an acknowledgment from the receiver
that some or all of the data has been received. If the
receiver acknowledges that all the data has been received
then the sender is free to send another 64 KB.
One way to improve the reliability of the TCP connection
is to reduce the window size that the receiver needs
to receive before sending an acknowledgement. However,
this will reduce throughput as more segments and acknowledgements
will need to be sent in order to transfer the same amount