Test Information:
Total Questions: 180
Test Number: 200-125
Vendor Name: Cisco
Cert Name: CCNA
Test Name: Cisco Certified Network Associate
Official Site: http://www.certsgrade.com
For
More Details: http://www.certsgrade.com/pdf/200-125/
Question: 1
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.
Answer: A, C, F
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.
Question: 2
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.
Answer: B, D, E
Explanation:
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.
Question: 3
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
Answer: E
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.
Question: 4
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.
Answer: A, D, E
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.
Question: 5
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
Answer: B
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:
Question: 6
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
Answer: A
Explanation:
FTP belongs to Application layer and
it is also the highest layer of the OSI model.
Question: 7
Refer to the exhibit.
After HostA pings HostB, which entry
will be in the ARP cache of HostA to support this transmission?
Answer: A
Explanation:
Host A knows host B is in another
network so it will send the pings to its default gateway 192.168.6.1. Host A
sends a broadcast frame asking the MAC address of 192.168.6.1. This information
(IP and MAC address of the default gateway) is saved in its ARP cache for later
use.
Question: 8
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.
Answer: C
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).
Question: 9
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
Answer: D
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.
Question: 10
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.
Answer: A, D
Explanation:
The transport layer segments data
into smaller pieces for transport. Each segment is assigned a sequence number,
so that the receiving device can reassemble the data on arrival.
The transport layer also use flow
control to maximize the transfer rate while minimizing the requirements to
retransmit. For example, in TCP, basic flow control is implemented by
acknowledgment by the receiver of the receipt of data; the sender waits for
this acknowledgment before sending the next part.
The Network layer (Layer 3) has two
key responsibilities. First, this layer controls the logical addressing of
devices. Second, the network layer determines the best path to a particular
destination network, and routes the data appropriately.
Question: 11
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
Answer: A
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.
Question: 12
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.
Answer: C, D
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.
Question: 13
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.
Answer: B, D, E
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.
Question: 14
Where does routing occur within the
DoD TCP/IP reference model?
A. application
B. internet
C. network
D. transport
Answer: B
Explanation:
The picture below shows the
comparison between TCP/IP model & OSI model. Notice that the Internet Layer
of TCP/IP is equivalent to the Network Layer which is responsible for routing
decision.
Question: 15
Refer to exhibit:
Which two destination addresses will
be used by Host A to send data to Host C? (Choose two.)
A. the IP address of Switch 1
B. the MAC address of Switch 1
C. the IP address of Host C
D. the MAC address of Host C
E. the IP address of the router's E0
interface
F. the MAC address of the router's E0
interface
Answer: C, F
Explanation:
While transferring data through many
different networks, the source and destination IP addresses are not changed.
Only the source and destination MAC addresses are changed. So in this case Host
A will use the IP address of Host C and the MAC address of E0 interface to send
data. When the router receives this data, it replaces the source MAC address
with its own E1 interface’s MAC address and replaces the destination MAC
address with Host C’s MAC address before sending to Host C.
Question: 16
For what two purposes does the
Ethernet protocol use physical addresses? (Choose two.)
A. to uniquely identify devices at
Layer 2
B. to allow communication with
devices on a different network
C. to differentiate a Layer 2 frame
from a Layer 3 packet
D. to establish a priority system to
determine which device gets to transmit first
E. to allow communication between
different devices on the same network
F. to allow detection of a remote
device when its physical address is unknown
Answer: A, E
Explanation:
Physical addresses or MAC addresses
are used to identify devices at layer 2.
MAC addresses are only used to
communicate on the same network. To communicate on different network we have to
use Layer 3 addresses (IP addresses) -> B is not correct.
Layer 2 frame and Layer 3 packet can
be recognized via headers. Layer 3 packet also contains physical address ->.
On Ethernet, each frame has the same
priority to transmit by default ->.
All devices need a physical address
to identify itself. If not, they cannot communicate ->.
Question: 17
Refer to the exhibit.
Based on the information given,
which switch will be elected root bridge and why?
A. Switch A, because it has the
lowest MAC address
B. Switch A, because it is the most
centrally located switch
C. Switch B, because it has the
highest MAC address
D. Switch C, because it is the most
centrally located switch
E. Switch C, because it has the
lowest priority
F. Switch D, because it has the highest
priority
Answer: E
Explanation:
To elect the root bridge in the LAN,
first check the priority value. The switch having the lowest priority will win
the election process. If Priority Value is the same then it checks the MAC
Address; the switch having the lowest MAC Address will become the root bridge.
In this case, switch C has the lowest MAC Address so it becomes the root
bridge.
Question: 18
Which of the following statements
describe the network shown in the graphic? (Choose two.)
A. There are two broadcast domains
in the network.
B. There are four broadcast domains
in the network.
C. There are six broadcast domains
in the network.
D. There are four collision domains
in the network.
E. There are five collision domains
in the network.
F. There are seven collision domains
in the network.
Answer: A, F
Explanation:
Only router can break up broadcast
domains so in the exhibit there are 2 broadcast domains: from e0 interface to
the left is a broadcast domain and from e1 interface to the right is another
broadcast domain ->.
Both router and switch can break up
collision domains so there is only 1 collision domain on the left of the router
(because hub doesn’t break up collision domain) and there are 6 collision
domains on the right of the router (1 collision domain from e1 interface to the
switch + 5 collision domains for 5 PCs in Production) ->.
Question: 19
In an Ethernet network, under what
two scenarios can devices transmit? (Choose two.)
A. when they receive a special token
B. when there is a carrier
C. when they detect no other devices
are sending
D. when the medium is idle
E. when the server grants access
Answer: C, D
Explanation:
Ethernet network is a shared
environment so all devices have the right to access to the medium. If more than
one device transmits simultaneously, the signals collide and cannot reach the
destination.
If a device detects another device
is sending, it will wait for a specified amount of time before attempting to
transmit.
When there is no traffic detected, a
device will transmit its message. While this transmission is occurring, the
device continues to listen for traffic or collisions on the LAN. After the
message is sent, the device returns to its default listening mode.
Question: 20
A router has two Fast Ethernet
interfaces and needs to connect to four VLANs in the local network. How can you
accomplish this task, using the fewest physical interfaces and without
decreasing network performance?
A. Use a hub to connect the four
VLANS with a Fast Ethernet interface on the router.
B. Add a second router to handle the
VLAN traffic.
C. Add two more Fast Ethernet
interfaces.
D. Implement a router-on-a-stick
configuration.
Answer: D
Explanation:
A router on a stick allows you to
use sub-interfaces to create multiple logical networks on a single physical
interface.
Test Information:
Total Questions: 180
Test Number: 200-125
Vendor Name: Cisco
Cert Name: CCNA
Test Name: Cisco Certified Network Associate
Official Site: http://www.certsgrade.com
For
More Details: http://www.certsgrade.com/pdf/200-125/
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