Vendor Name: Cisco
Exam code: 200-120
Exam Name: CCNA Cisco Certified Network Associate CCNA (803)
Click the link below to get full version
http://www.certifyguide.com/exam/200-120/
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Question: 1
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Refer to
the exhibit:
What will
Router1 do when it receives the data frame shown? (Choose three.)
A. Router1
will strip off the source MAC address and replace it with the MAC address
0000.0c36.6965.
B. Router1
will strip off the source IP address and replace it with the IP address
192.168.40.1.
C. Router1
will strip off the destination MAC address and replace it with the MAC address
0000.0c07.4320.
D. Router1
will strip off the destination IP address and replace it with the IP address of
192.168.40.1.
E. Router1
will forward the data packet out interface FastEthernet0/1.
F. Router1
will forward the data packet out interface FastEthernet0/2.
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Answer: A, C, F
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Explanation:
Remember,
the source and destination MAC changes as each router hop along with the TTL
being decremented but the source and destination IP address remain the same from
source to destination.
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Question: 2
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Refer to
the exhibit.
Which three
statements correctly describe Network Device A? (Choose three.)
A. With a
network wide mask of 255.255.255.128, each interface does not require an IP
address.
B. With a
network wide mask of 255.255.255.128, each interface does require an IP address
on a unique IP subnet.
C. With a
network wide mask of 255.255.255.0, must be a Layer 2 device for the PCs to
communicate with each other.
D. With a
network wide mask of 255.255.255.0, must be a Layer 3 device for the PCs to
communicate with each other.
E. With a
network wide mask of 255.255.254.0, each interface does not require an IP
address.
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Answer: B, D, E
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If Subnet
Mask is 255.255.255.128 the hosts vary from x.x.x.0 - x.x.x.127 & x.x.x.128- x.x.x.255,so the
IP Addresses of 2 hosts fall in
different subnets so each interface needs an IP an address so that they can communicate each other.
If Subnet
Mask is 255.255.255.0 the 2 specified hosts fall in different subnets so they
need a Layer 3 device to communicate.
If Subnet
Mask is 255.255.254.0 the 2 specified hosts are in same subnet so are in network address and can be
accommodated in same Layer 2 domain and
can communicate with each other directly using the Layer 2 address.
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Question: 3
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Which layer
in the OSI reference model is responsible for determining the availability of
the receiving program and checking to see if enough resources exist for that communication?
A.
transport
B. network
C.
presentation
D. session
E.
application
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Answer: E
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Explanation:
This
question is to examine the OSI reference model.
The
Application layer is responsible for identifying and establishing the
availability of the intended communication partner and determining whether
sufficient resources for the intended communication exist.
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Question: 4
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Which of
the following describes the roles of devices in a WAN? (Choose three.)
A. A
CSU/DSU terminates a digital local loop.
B. A modem
terminates a digital local loop.
C. A
CSU/DSU terminates an analog local loop.
D. A modem
terminates an analog local loop.
E. A router
is commonly considered a DTE device.
F. A router
is commonly considered a DCE device.
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Answer: A, D, E
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Explanation:
The idea
behind a WAN is to be able to connect two DTE networks together through a DCE
network. The network’s DCE device (includes CSU/DSU) provides clocking to the
DTE-connected interface (the router’s serial interface).
A modem
modulates outgoing digital signals from a computer or other digital device to
analog signals for a conventional copper twisted pair telephone line and
demodulates the incoming analog signal and converts it to a digital signal for
the digital device. A CSU/DSU is used between two digital lines -
For more
explanation of answer D, in telephony the local loop (also referred to as a
subscriber line) is the physical link or circuit that connects from the
demarcation point of the customer premises to the edge of the carrier or
telecommunications service provider’s network. Therefore a modem terminates an
analog local loop is correct.
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Question: 5
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Refer to
the exhibit.
Host A
pings interface S0/0 on router 3. What is the TTL value for that ping?
A. 252
B. 253
C. 254
D. 255
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Answer: B
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Explanation:
From the
CCNA ICND2 Exam book: “Routers decrement the TTL by 1 every time they forward a
packet; if a router decrements the TTL to 0, it throws away the packet. This
prevents packets from rotating forever.” I want to make it clear that before
the router forwards a packet, the TTL is still remain the same. For example in
the topology above, pings to S0/1 and S0/0 of Router 2 have the same TTL.
The picture
below shows TTL values for each interface of each router and for Host B. Notice
that Host A initializes ICMP packet with a TTL of 255:
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Question: 6
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A network
administrator is verifying the configuration of a newly installed host by
establishing an FTP connection to a remote server. What is the highest layer of
the protocol stack that the network administrator is using for this operation?
A.
application
B.
presentation
C. session
D.
transport
E. internet
F. data
link
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Answer: A
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Explanation:
FTP belongs
to Application layer and it is also the highest layer of the OSI model.
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Question: 7
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Refer to
the exhibit.
After HostA
pings HostB, which entry will be in the ARP cache of HostA to support this
transmission?
A.
B.
C.
D.
E.
F.
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Answer: A
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Explanation:
When a host
needs to reach a device on another subnet, the ARP cache entry will be that of
the Ethernet address of the local router (default gateway) for the physical MAC
address. The destination IP address will
not change, and will be that of the remote host (HostB).
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Question: 8
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A network
interface port has collision detection and carrier sensing enabled on a shared
twisted pair network. From this statement, what is known about the network
interface port?
A. This is
a 10 Mb/s switch port.
B. This is
a 100 Mb/s switch port.
C. This is
an Ethernet port operating at half duplex.
D. This is
an Ethernet port operating at full duplex.
E. This is
a port on a network interface card in a PC.
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Answer: C
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Explanation:
Modern
Ethernet networks built with switches and full-duplex connections no longer
utilize CSMA/CD. CSMA/CD is only used in obsolete shared media Ethernet (which
uses repeater or hub).
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Question: 9
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A receiving
host computes the checksum on a frame and determines that the frame is damaged.
The frame is then discarded. At which OSI layer did this happen?
A. session
B.
transport
C. network
D. data
link
E. physical
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Answer: D
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Explanation:
The Data
Link layer provides the physical transmission of the data and handles error
notification, network topology, and flow control. The Data Link layer formats
the message into pieces, each called a data frame, and adds a customized header
containing the hardware destination and source address. Protocols Data Unit
(PDU) on Datalink layer is called frame. According to this question the frame
is damaged and discarded which will happen at the Data Link layer.
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Question: 10
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Which of
the following correctly describe steps in the OSI data encapsulation process?
(Choose two.)
A. The
transport layer divides a data stream into segments and may add reliability and
flow control information.
B. The data
link layer adds physical source and destination addresses and an FCS to the
segment.
C. Packets
are created when the network layer encapsulates a frame with source and
destination host addresses and protocol-related control information.
D. Packets
are created when the network layer adds Layer 3 addresses and control information
to a segment.
E. The
presentation layer translates bits into voltages for transmission across the
physical link.
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Answer: A, D
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Explanation:
The
Application Layer (Layer 7) refers to communications services to applications
and is the interface between the network and the application. Examples include.
Telnet, HTTP, FTP, Internet browsers, NFS, SMTP gateways, SNMP, X.400 mail, and
FTAM.
The
Presentation Layer (Layer 6) defining data formats, such as ASCII text, EBCDIC
text, binary, BCD, and JPEG. Encryption also is defined as a presentation layer
service. Examples include. JPEG, ASCII, EBCDIC, TIFF, GIF, PICT, encryption,
MPEG, and MIDI.
The Session
Layer (Layer 5) defines how to start, control, and end communication sessions.
This includes the control and management of multiple bidirectional messages so
that the application can be notified if only some of a series of messages are
completed. This allows the presentation layer to have a seamless view of an
incoming stream of data. The presentation layer can be presented with data if
all flows occur in some cases. Examples include. RPC, SQL, NFS, NetBios names,
AppleTalk ASP, and DECnet SCP
The
Transport Layer (Layer 4) defines several functions, including the choice of
protocols. The most important Layer 4 functions are error recovery and flow
control. The transport layer may provide for retransmission, i.e., error
recovery, and may use flow control to prevent unnecessary congestion by
attempting to send data at a rate that the network can accommodate, or it might
not, depending on the choice of protocols. Multiplexing of incoming data for
different flows to applications on the same host is also performed. Reordering
of the incoming data stream when packets arrive out of order is included. Examples
include. TCP, UDP, and SPX.
The Network
Layer (Layer 3) defines end-to-end delivery of packets and defines logical
addressing to accomplish this. It also defines how routing works and how routes
are learned; and how to fragment a packet into smaller packets to accommodate
media with smaller maximum transmission unit sizes. Examples include. IP, IPX,
AppleTalk DDP, and ICMP. Both IP and IPX define logical addressing, routing,
the learning of routing information, and end-to-end delivery rules. The IP and IPX
protocols most closely match the OSI network layer (Layer 3) and are called
Layer 3 protocols because their functions most closely match OSI's Layer 3.
The Data
Link Layer (Layer 2) is concerned with getting data across one particular link
or medium. The data link protocols define delivery across an individual link.
These protocols are necessarily concerned with the type of media in use.
Examples includE. IEEE 802.3/802.2, HDLC, Frame Relay, PPP, FDDI, ATM, and IEEE
802.5/802.2.
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Question: 11
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Refer to
the graphic.
Host A is
communicating with the server. What will be the source MAC address of the
frames received by Host A from the server?
A. the MAC
address of router interface e0
B. the MAC
address of router interface e1
C. the MAC
address of the server network interface
D. the MAC
address of host A
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Answer: A
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Explanation:
Whereas
switches can only examine and forward packets based on the contents of the MAC
header, routers can look further into the packet to discover the network for
which a packet is destined. Routers make forwarding decisions based on the
packet's network-layer header (such as an IPX header or IP header). These
network-layer headers contain source and destination network addresses. Local
devices address packets to the router's MAC address in the MAC header. After
receiving the packets, the router must perform the following steps:
1. Check
the incoming packet for corruption, and remove the MAC header . The router
checks the packet for MAC-layer errors. The router then strips off the MAC
header and examines the network-layer header to determine what to do with the
packet.
2. Examine
the age of the packet. The router must ensure that the packet has not come too
far to be forwarded. For example, IPX headers contain a hop count. By default,
15 hops is the maximum number of hops (or routers) that a packet can cross. If
a packet has a hop count of 15, the router discards the packet. IP headers
contain a Time to Live (TTL) value. Unlike the IPX hop count, which increments
as the packet is forwarded through each router, the IP TTL value decrements as
the IP packet is forwarded through each router. If an IP packet has a TTL value
of 1, the router discards the packet. A router cannot decrement the TTL value
to 1 and then forward the packet.
3.
Determine the route to the destination. Routers maintain a routing table that lists
available networks, the direction to the desired network (the outgoing
interface number), and the distance to those networks. After determining which
direction to forward the packet, the router must build a new header. (If you
want to read the IP routing tables on a Windows 95/98 workstation, type ROUTE
PRINT in the DOS box.)
4. Build
the new MAC header and forward the packet. Finally, the router builds a new MAC
header for the packet. The MAC header includes the router's MAC address and the
final destination's MAC address or the MAC address of the next router in the
path.
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Question: 12
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Refer to
the exhibit.
What two
results would occur if the hub were to be replaced with a switch that is
configured with one Ethernet VLAN? (Choose two.)
A. The
number of collision domains would remain the same.
B. The
number of collision domains would decrease.
C. The
number of collision domains would increase.
D. The
number of broadcast domains would remain the same.
E. The
number of broadcast domains would decrease.
F. The
number of broadcast domains would increase.
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Answer: C, D
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Explanation:
Basically,
a collision domain is a network segment that allows normal network traffic to
flow back and forth. In the old days of hubs, this meant you had a lot of
collisions, and the old CSMA/CD would be working overtime to try to get those
packets re-sent every time there was a collision on the wire (since ethernet
allows only one host to be transmitting at once without there being a traffic jam).
With switches, you break up collision domains by switching packets bound for
other collision domains. These days, since we mostly use switches to connect
computers to the network, you generally have one collision domain to a PC.
Broadcast
domains are exactly what they imply: they are network segments that allow
broadcasts to be sent across them. Since switches and bridges allow for
broadcast traffic to go unswitched, broadcasts can traverse collision domains
freely. Routers, however, don't allow broadcasts through by default, so when a
broadcast hits a router (or the perimeter of a VLAN), it doesn't get forwarded.
The simple way to look at it is this way: switches break up collision domains,
while routers (and VLANs) break up collision domains and broadcast domains.
Also, a broadcast domain can contain multiple collision domains, but a
collision domain can never have more than one broadcast domain associated with
it.
Collision
Domain: A group of Ethernet or Fast Ethernet devices in a CSMA/CD LAN that are
connected by repeaters and compete for access on the network. Only one device
in the collision domain may transmit at any one time, and the other devices in
the domain listen to the network in order to avoid data collisions. A collision
domain is sometimes referred to as an Ethernet segment.
Broadcast
Domain: Broadcasting sends a message to everyone on the local network (subnet).
An example for Broadcasting would be DHCP Request from a Client PC. The Client
is asking for a IP Address, but the client does not know how to reach the DHCP
Server. So the client sends a DHCP Discover packet to EVERY PC in the local
subnet (Broadcast). But only the DHCP Server will answer to the Request.
How to
count them?
Broadcast
Domain:
No matter
how many hosts or devices are connected together, if they are connected with a
repeater, hub, switch or bridge, all these devices are in ONE Broadcast domain
(assuming a single VLAN). A Router is used to separate Broadcast-Domains (we
could also call them Subnets - or call them VLANs).
So, if a
router stands between all these devices, we have TWO broadcast domains.
Collision
Domain:
Each
connection from a single PC to a Layer 2 switch is ONE Collision domain. For
example, if 5 PCs are connected with separate cables to a switch, we have 5
Collision domains. If this switch is connected to another switch or a router,
we have one collision domain more.
If 5
Devices are connected to a Hub, this is ONE Collision Domain. Each device that
is connected to a Layer 1 device (repeater, hub) will reside in ONE single
collision domain.
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Question: 13
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Which three
statements accurately describe Layer 2 Ethernet switches? (Choose three.)
A. Spanning
Tree Protocol allows switches to automatically share VLAN information.
B. Establishing
VLANs increases the number of broadcast domains.
C. Switches
that are configured with VLANs make forwarding decisions based on both Layer 2
and Layer 3 address information.
D.
Microsegmentation decreases the number of collisions on the network.
E. In a
properly functioning network with redundant switched paths, each switched
segment will contain one root bridge with all its ports in the forwarding
state. All other switches in that broadcast domain will have only one root
port.
F. If a
switch receives a frame for an unknown destination, it uses ARP to resolve the
address.
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Answer: B, D, E
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Explanation:
Microsegmentation
is a network design (functionality) where each workstation or device on a
network gets its own dedicated segment (collision domain) to the switch. Each
network device gets the full bandwidth of the segment and does not have to
share the segment with other devices. Microsegmentation reduces and can even
eliminate collisions because each segment is its own collision domain -> .
Note:
Microsegmentation decreases the number of collisions but it increases the
number of collision domains.
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Question: 14
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Where does
routing occur within the DoD TCP/IP reference model?
A.
application
B. internet
C. network
D.
transport
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Answer: B
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