Tài liệu Exam :640-607 Cisco Certified Network Associate - Version 1-2003 pptx

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QUESTION NO: 4
The IP address 131.107.0.0 is a class B address. What is the range of binary values for the first octet in
this address class?

A. 10000000-11111111
B. 00000000-10111111
C. 10000000-10111111
D. 10000000-11011111
E. 11000000-11101111


Answer: C
Explanation: Class B addresses have a range of 128 – 191. One of these numbers would appear in the first
octet of a Class B address. 128 and 191 are converted to binary below:

128 64 32 16 8 4 2 1
128 1 0 0 0 0 0 0 0
191 1 0 1 1 1 1 1 1

Therefore the first octet converted to binary is 10000000 – 10111111.

Incorrect Answers
A: The 10000000-11111111 range, 128-255, does not define an address class.
B: The 00000000-10111111 range, 0-191, does not define an address class.
D: The 10000000-11011111 range, 128-223, does not define an address class.
E: The 11000000-11101111 range, 192-239, does not define an address class.

Steve McQuerry. Interconnecting Cisco Network Devices
. (Cisco Press: 2000) pages 220 – 223.



QUESTION NO: 5
TCP is a connection-oriented protocol. An advantage of operating in a connection-oriented environment
is that a connection is established between both ends before the transfer of information can begin. What
is a disadvantage of using a connection-oriented protocol such as TCP?

A. Packet acknowledgement may add overhead.
B. Packets are not tagged with sequence numbers.
C. Loss or duplication of data packets is more likely to occur.
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D. The application layer must assume responsibility for correct sequencing of the data packets.


Answer: A.
Explanation: One of the benefits of a connection-orientated protocol is that there is a guarantee of delivery of
data. This guarantee is provided as the two communicating exchange PDUs during transmission and if an
acknowledgement is not received then the data is retransmitted. As can be imagined this exchange of PDUs can
cause an increase in overhead.

Incorrect Answers:
B: Sequence numbers are added to insure correct order
C: Packet loss, duplication, and ordering are handled by connection-oriented protocols.
D: The transport layer (such as TCP) handles sequencing.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 29-30.



QUESTION NO: 6
Switches have three primary modes to handle frame switching. Which one of these modes looks at the
destination address and then immediately forwards the frame to the destination?

A. CSMA/CD
B. FULL DUPLEX
C. CUT THROUGH
D. HALF DUPLEX
E. FRAGMENTATION
F. STORE AND FORWARD


Answer: C.
Explanation:
In cut-through mode, the switch checks the destination address (DA) as soon as the header is received and
immediately begins forwarding the frame. Depending on the network transport protocol being used (connection
or connectionless orientate), there is a significant decrease in latency from input port to output port. The delay
in cut-through switching remains constant regardless of the size of the frame, because this switching mode starts
to forward the frame as soon as the switch reads the DA.

Incorrect Answers:
A: CSMA/CD is not a method of transporting frames. Rather it is a set of rules that are used to determine how
network devices will respond to two different devices attempting to communicate on a data channel at the
same time.
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B: Full duplex refers to how two switches communicate with each other. In this case, there is a transmission of
data in two directions at the same time.
D: Half duplex refers to how two switches communicate with each other. With half duplex the communication
can only be in one direction and if not a collision will occur.
E: This is not a method of frame communication.
F: In store and forward the entire frame must first be received before it can be forwarded on.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 162-5.



QUESTION NO: 7
Which of the following are Application layer protocols that use TCP/IP? (Choose three.)

A. ARP
B. HTTP
C. SMTP
D. FTP
E. ICMP


Answer: B, C, D
Explanation: There are a number of TCP/IP application layer protocols. The common TCP/IP application
layer protocols include: FTP, Telnet, SMTP, and HTTP.

Incorrect Answers:

A. ARP operates at the Internetwork layer of the TCP/IP protocol stack.
E. ICMP operates at the Internetwork layer of the TCP/IP protocol stack.

Steve McQuerry. Interconnecting Cisco Network Devices
. (Cisco Press: 2000) pages 206 – 215.



QUESTION NO: 8
Two types of frame tagging are ISL and 802.lQuestion No: What is the purpose of Frame Tagging?

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A. They provide best path determination.
B. They allow the exchange of filtering tables.
C. They specify different implementation of the Spanning-Tree Protocol.
D. They provide inter-switch VLAN communication.


Answer: D
Explanation: The purpose of frame tagging (ISL tagging) is to interconnect multiple switches and to keep
VLAN information as it goes through various switches.

Incorrect Answers:

A, B, and C. This are not the purposed for frame tagging.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 186 – 187.



QUESTION NO: 9
You company has decided to use RIP version 1 as the routing on a Cisco router. What is the command to
enable rip as the routing protocol on the company’s router?


Answer: Router rip
Explanation: The key characteristics of RIP include: it is a distance vector protocol, hop count is the metric
used for path selection, it maximum allowable hop count is 15, it broadcasts it entire routing table every 30
seconds by default and it can be load balanced as many as six equal cost paths (4 paths are the default). To
configure RIP not only does the router rip command need to be inputted but also it must be followed by the
network command. The network command must be issued for each directly connected network.

Steve McQuerry. Interconnecting Cisco Network Devices
. (Cisco Press: 2000) pages 278-279.



QUESTION NO: 10
Your company has decided to use IP RIP version 1 as the routing protocol. Which of the following are
the commands you can use to configure IP RIP version 1 on your router?

A. Router RIP
network 172.16.1.0
network 10.1.0.1
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B. Router RIP
network 172.16.0.0
network 10.0.0.0
C. Router RIP
network 172.16.1.0 172.16.1.1
network 10.1.0.0 10.1.1.1
D. Router RIP
network 172.16.1.0 265.255.255.0
Network 10.1.0.0 255.255.0.0


Answer: B.
Explanation: To enable RIP version 1 not only does the router rip command need to be used but also it must be
followed by the network command. The network command must be issued for each directly connected
network. The network command must be followed by a valid network address.

Incorrect Answers:
A: Is this series of commands the network 10.1.0.1 is not a valid command.
C: If 4 networks are directly connected they must have their own network command.
D: There is no need to include a subnet mask with a network command.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 278-9.



QUESTION NO: 11
Spanning-Tree was originally developed by DEC. What is the reason Spanning-Tree is used in a
switched LAN?

A. To provide a mechanism for network monitoring in switched environments.
B. To prevent routing loops in networks with redundant paths.
C. To prevent routing switching loops in networks with redundant switched paths.
D. To manage, the addition, deletion, and naming of VLANs across multiple switches.
E. To segment a network into multiple collision domains.


Answer: B.
Explanation: The purpose of the Spanning Tree Protocol (STP) is to provide for redundant paths within a
switched environment while ensuring that there is a loop free network. This is done as the redundant ports are
blocked.
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Incorrect Answers:
A. STP does not provide mechanism to monitor a switched network.
C. Loops are not referred to as “routing switching loops”.
D. STP is not used for VLAN management.
E. Switches create multiple collisions domains and not STP.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 155-156.



QUESTION NO: 12
Switches have three primary modes to handle frame switching. Which two statements about the store
and forward switching method are true? (Choose two)

A. Latency remains constant regardless of frame size.
B. Latency through the switch varies with frame length.
C. The switch receives the complete frame before beginning to forward it.
D. The switch checks the destination address as soon as it receives the header and begins forwarding the
frame immediately.


Answer B, C.
Explanation:
In store and forward mode, the switch must receive the complete frame before forwarding takes place. The
destination and source addresses are read, the cyclic redundancy check (CRC) is performed, relevant filters are
applied, and the frame is forwarded. If the CRC is bad, the frame is discarded. The latency (or delay) through
the switch varies with frame length.

Incorrect Answers:
A: Is wrong because the latency changes with the frame size.
D: Is wrong because it waits for the complete name and not merely the destination address.

Steve McQuerry. Interconnecting Cisco Network Devices
. (Cisco Press: 2000) page 162.



QUESTION NO: 13
Acme Ltd. consists of three campuses: North, Main and South. They have purchased three 2501 routers.
Each router has one Ethernet interface and two serial interfaces. Each campus is connected serially to its
neighbor. The routers have been working properly.
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The connection between North and Main ceases operation one day and an unauthorized entry is detected
on the South router.
Determine the problem and restore connectivity. The network has been configured with the following
characteristics:

The routers are named North, Main, South.
All networks have the default subnet mask.
RIP is the routing protocol.
The clocking signal is provided on the serial 0 interface.


Lab 1
Name: North
E0: 192.168.159.1
S0: 192.168.75.1
Secret password : testk

Lab 2
Name: Main
E0: 192.168.112.1
S0: 192.168.201.1
S1: 192.168.75.2
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Secret password : testk

Lab 3
Name: South
E0: 192.168.65.1
S1: 192.168.201.2
Secret password : testk

Start by clicking on host that is connected to the router you want to configure.

Answer Lab 1:
<Click on Host2, which is connected to the Lab 1 router>
enable
config terminal
hostname North
enable secret testk
interface ethernet 0
ip address 192.168.159.1 255.255.255.0
no shutdown
exit
interface serial 0
ip address 192.168.75.1 255.255.255.0
clock rate 64000
no shutdown
exit
router rip
network 192.168.159.0
network 192.168.75.0
^z
copy running-config startup-config

Explanation:
Note: comments are added in text after the !-sign. They will not be shown during simulation.
First we click on the Lab 1 router.

Router Con0 is now available ! The router starts
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Press RETURN to get started. ! Here we press return



Router>enable
! We must enter EXEC mode (or enable mode as it also called)
Router#config terminal ! We must enter configuration mode.
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)#hostname North ! We change the host name
North(config)#enable secret testk ! We set the password
North(config)#interface ethernet 0 ! We enter interface configuration mode for ethernet 0
North(config-if)#ip address 192.168.159.1 255.255.255.0 ! We set the IP address for Ethernet 0.
! Note that we use a 24 bit network mask.
!It is a class C address.
North(config-if)#no shutdown ! We start the interface
%LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0, changed state to up
%LINK-3-UPDOWN: Interface Ethernet0, changed state to up

North(config-if)#exit
! We exit interface configuration for Ethernet 0
North(config)#interface serial0 ! We enter interface configuration mode for the serial0 interface.
! Note that there are no space in serial0
North(config-if)#ip address 192.168.75.1 255.255.255.0 ! IP address for serial0
! Cisco recommends to set the IP address of the interface before
! setting the clockrate
North(config-if)#clock rate 64000 ! We set a clockrate. We must do it to enable communication between
! the routers. They must be synchronized.
North(config-if)#no shutdown ! Start the serial0 interface
%LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0, changed state to up
%LINK-3-UPDOWN: Interface Serial0, changed state to up

North(config-if)#exit
! Exit interface configuration mode
North(config)#router rip ! Start the routing protocol. RIP does not need further configuration.
! RIP works well in this small network.
! We enter router configuration mode.
North(config-router)#network 192.168.159.0 ! We enable RIP on the network of Ethernet E0.
North(config-router)#network 192.168.75.0 ! We enable RIP on the network of Serial0.
North(config-router)#^Z
! We exit configuration mode and return to enable mode.
%SYS-5-CONFIG_I: Configured from console by console
North#copy running-config startup-config
! We save our configurations to NVRAM
Destination filename [startup-config]? ! We confirm with Enter.
North# ! We are finished.

You don't need to make full configuration because all routers have already been configured but they have some
mistakes. Your task is to find these mistakes and fix them. Maybe the easy way is to remember full config, but
better is to understand the right configuration. You need to add two networks for Lab 1 as we only have to add
the networks we have on the router. For LAB 2 we add three networks, and for LAB 3 we add two networks.
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Wendell Odom. Cisco CCNA Exam #640-507 Certification Guide. (Cisco Press: 2000) pages 374-403.

Note: If you are unsure of the testing environment, try the following address:
http://www.cisco.com/warp/public/10/wwtraining/certprog/testing/simulation/demo_sim.html
************************************
Answer Lab 2:

enable
config terminal
hostname Main
enable secret testk
interface ethernet 0
ip address 192.168.112.1 255.255.255.0
no shutdown
exit
interface serial 0
ip address 192.168.201.1 255.255.255.0
clock rate 64000
no shutdown
exit
interface serial 1
ip address 192.168.75.2 255.255.255.0
no shutdown
exit
router rip
network 192.168.75.0
network 192.168.112.0
network 192.168.201.0^z
copy running-config startup-config


Explanation: Very similar to Lab 1. We have two serial interfaces in lab 2 to configure. We must also make
sure that we enable RIP on all three interfaces with the network command.
******************************************
Answer Lab 3:
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