Interconnecting Cisco Networking Devices Part 1 v3.0 (ICND1)

 

QUESTION 31

How does TCP differ from UDP? (Choose two.)

 

A.

TCP provides best effort delivery.

B.

TCP provides synchronized communication.

C.

TCP segments are essentially datagrams.

D.

TCP provides sequence numbering of packets.

E.

TCP uses broadcast delivery.

 

Correct Answer: BD

Explanation:

Because TCP is a connection-oriented protocol responsible for ensuring the transfer of a datagram from the source to destination machine (end-to-end communications), TCP must receive communications messages from the destination machine to acknowledge receipt of the datagram. The term virtual circuit is usually used to refer to the handshaking that goes on between the two end machines, most of which are simple acknowledgment messages (either confirmation of receipt or a failure code) and datagram sequence numbers. Rather than impose a state within the network to support the connection, TCP uses synchronized state between the two endpoints. This synchronized state is set up as part of an initial connection process, so TCP can be regarded as a connection-oriented protocol. Much of the protocol design is intended to ensure that each local state transition is communicated to, and acknowledged by, the remote party.

Reference: http://en.wikibooks.org/wiki/Communication_Networks/TCP_and_UDP_Protocols

 

 

QUESTION 32

Refer to the exhibit. Mary is sending an instant message to Robert. The message will be broken into a series of packets that will traverse all network devices. What addresses will populate these packets as they are forwarded from Router1 to Router2?

 

clip_image002

clip_image004

 

A.

Option A

B.

Option B

C.

Option C

D.

Option D

E.

Option E

 

Correct Answer: B

Explanation:

The Source and Destination IP address is not going to change. Host 1 IP address will stay as being the source IP and the Host 2 IP address will stay the destination IP address.

Those two are not going to change.

For the MAC address it is going to change each time it goes from one hope to another.

(Except switches… they don’t change anything)

Frame leaving HOST 1 is going to have a source MAC of Host 1 and a destination MAC of Router 1.

Router 1 is going to strip that info off and then will make the source MAC address of Router1’s exiting interface, and making Router2’s interface as the destination MAC address.

Then the same will happen… Router2 is going to change the source/destination info to the source MAC being the Router2 interface that it is going out, and the destination will be Host2’s MAC address.

 

 

QUESTION 33

Which OSI layer header contains the address of a destination host that is on another network?

 

A.

application

B.

session

C.

transport

D.

network

E.

data link

F.

physical

 

Correct Answer: D

Explanation:

Only network address contains this information. To transmit the packets the sender uses network address and datalink address. But the layer 2 address represents just the address of the next hop device on the way to the sender. It is changed on each hop. Network address remains the same.

 

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QUESTION 34

Refer to the exhibit. The exhibit is showing the topology and the MAC address table. Host A sends a data frame to host D. What will the switch do when it receives the frame from host A?

 

clip_image008

 

 

A.

The switch will add the source address and port to the MAC address table and forward the frame to host D.

B.

The switch will discard the frame and send an error message back to host A.

C.

The switch will flood the frame out of all ports except for port Fa0/3.

D.

The switch will add the destination address of the frame to the MAC address table and forward the frame to host D.

Correct Answer: A

Explanation:

When switch receives the data frame from the host not having the MAC address already on the MAC table, it will add the MAC address to source port on MAC address table and sends the data frame.

 

 

QUESTION 35

Refer to the exhibit. As packets travel from Mary to Robert, which three devices will use the destination MAC address of the packet to determine a forwarding path? (Choose three.)

 

clip_image010

 

A.

Hub1

B.

Switch1

C.

Router1

D.

Switch2

E.

Router2

F.

Switch3

 

Correct Answer: BDF

Explanation:

Switches use the destination MAC address information for forwarding traffic, while routers use the destination IP address information.

Local Area Networks employ Layer 2 Switches and Bridges to forward and filter network traffic. Switches and Bridges operate at the Data Link Layer of the Open System Interconnect Model (OSI). Since Switches and Bridges operate at the Layer 2 they operate more intelligently than hubs, which work at Layer 1 (Physical Layer) of the OSI. Because the switches and bridges are able to listen to the traffic on the wire to e
xamine the source and destination MAC address. Being able to listen to the traffic also allows the switches and bridges to compile a MAC address table to better filter and forward network traffic. To accomplish the above functions switches and bridges carry out the following tasks:

MAC address learning by a switch or a bridge is accomplished by the same method. The switch or bridge listens to each device connected to each of its ports and scan the incoming frame for the source MAC address. This creates a MAC address to port map that is cataloged in the switches/bridge MAC database. Another name for the MAC address table is content addressable memory or CAM table.

When a switch or bridge is listening to the network traffic, it receives each frame and compares it to the MAC address table. By checking the MAC table the switch/ bridge are able o determine which port the frame came in on. If the frame is on the MAC table the frame is filtered or transmitted on only that port. If the switch determines that the frame is not on the MAC table, the frame is forwarded out to all ports except the incoming port.

 

 

QUESTION 36

Refer to the exhibit. Which option describes how SwitchA will handle the frame just received?

 

clip_image012

 

A.

It will drop the frame.

B.

It will forward the frame out of port Fa0/3 only.

C.

It will flood the frame out all ports.

D.

It will flood the frame out of all the ports except Fa0/3.

 

Correct Answer: D

 

 

QUESTION 37

Which of the following are types of flow control? (Choose three.)

 

A.

buffering

B.

cut-through

C.

windowing

D.

congestion avoidance

E.

load balancing

 

Correct Answer: ACD

Explanation:

During Transfer of data, a high speed computer is generating data traffic a lot faster than the network device can handle in transferring to destination, so single gateway or destination device cannot handle much amount of traffic that is called “Congestion”.

 

Buffering

The Technie is used to control the data transfer when we have congestion, when a network device receive a data it stores in memory section and then transfer to next destination this process called “Buffering”.

Windowing Whereas Windowing is used for flow control by the Transport layer. Say the sender device is sending segments and the receiver device can accommodate only a fixed number of segments before it can accept more, the two devices negotiate the window size during the connection setup.

This is done so that the sending device doesn’t overflow the receiving device’s buffer. Also the receiving device can send a single acknowledgement for the segments it has received instead of sending an acknowledgement after every segment received. Also, this window size is dynamic meaning, the devices can negotiate and change the window size in the middle of a session. So if initially the window size is three and the receiving device thinks that it can accept more number of segments in its buffer it can negotiate with the sending device and it increases it to say 5 for example. Windowing is used only by TCP since UDP doesn’t use or allow flow control.

 

Reference: http://www.info-it.net/cisco/ccna/exam-tips/flow-control.php

 

 

QUESTION 38

Which two characteristics apply to Layer 2 switches? (Choose two.)

 

A.

Increases the number of collision domains

B.

Decreases the number of collision domains

C.

Implements VLAN

D.

Decreases the number of broadcast domains

E.

Uses the IP address to make decisions for forwarding data packets

 

Correct Answer: AC

Explanation:

Layer 2 switches offer a number of benefits to hubs, such as the use of VLANs and each switch port is in its own separate collision domain, thus eliminating collisions on the segment.

 

 

QUESTION 39

Which transport layer protocol provides best-effort delivery service with no acknowledgment receipt required?

 

A.

HTTP

B.

IP

C.

TCP

D.

Telnet

E.

UDP

 

Correct Answer: E

Explanation:

UDP provides a connectionless datagram service that offers best-effort delivery, which means that UDP does not guarantee delivery or verify sequencing for any datagrams. A source host that needs reliable communication must use either TCP or a program that provides its own sequencing and acknowledgment services.

 

 

QUESTION 40

Which two characteristics describe the access layer of the hierarchical network design model? (Choose two.)

 

A.

layer 3 support

B.

port security

C.

redundant components

D.

VLANs

E.

PoE

 

Correct Answer: BD

Explanation:

Access layer

The main purpose of the access layer is to provide direct connection to devices on the network and controlling which devices are allowed to communicate over it. The access layer interfaces with end devices, such as PCs, printers, and IP phones, to provide access to the rest of the network. The access layer can include routers, switches, bridges, hubs, and wireless access points (AP).

 

Switch features in the Access layer:

 

clip_image014Port security

clip_image014[1]VLANs

clip_image014[2]Fast Ethernet/Gigabit Ethernet

clip_image014[3]Power over Ethernet (PoE)

clip_image014[4]Link aggregation

clip_image014[5]Quality of Service (QoS)

 

References:

http://www.ciscopath.com/content/61/

http://www.mcmcse.com/cisco/guides/hierarchical_model.shtml

 

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