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CCNA Routing and Switching v3.0

QUESTION 11

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

 

Correct Answer: AE

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 12

Refer to the exhibit. After HostA pings HostB, which entry will be in the ARP cache of HostA to support this transmission?

 

clip_image001

clip_image002

A.

Exhibit A

B.

Exhibit B

C.

Exhibit C

D.

Exhibit D

E.

Exhibit E

F.

Exhibit F

 

Correct 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 13

Host 1 is trying to communicate with Host 2. The e0 interface on Router C is down. Which of the following are true? (Choose two.)

 

clip_image003

 

A.

Router C will use ICMP to inform Host 1 that Host 2 cannot be reached.

B.

Router C will use ICMP to inform Router B that Host 2 cannot be reached.

C.

Router C will use ICMP to inform Host 1, Router A, and Router B that Host 2 cannot be reached.

D.

Router C will send a Destination Unreachable message type.

E.

Router C will send a Router Selection message type.

F.

Router C will send a Source Quench message type.

 

Correct Answer: AD

Explanation:

Host 1 is trying to communicate with Host 2. The e0 interface on Router C is down. Router C will send ICMP packets to inform Host 1 that Host 2 cannot be reached.

 

 

QUESTION 14

What is the difference between a CSU/DSU and a modem?

 

A.

A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line.

B.

A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line.

C.

A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line.

D.

A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line.

 

Correct Answer: D

Explanation:

CSU/DSU is used to convert digital signals from a router to a network circuit such as a T1, while a modem is used to convert digital signals over a regular POTS line.

 

 

QUESTION 15

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

 

Correct 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 16

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.

 

Correct Answer: AD

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 17

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.

 

Correct Answer: BDE

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 18

Where does routing occur within the DoD TCP/IP reference model?

 

A.

application

B.

internet

C.

net
work

D.

transport

 

Correct 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.

 

clip_image004

 

 

QUESTION 19

DRAG DROP

clip_image006

 

Correct Answer:

clip_image008

 

 

QUESTION 20

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

 

Correct 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.

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