CCNA v7

A network administrator is measuring the transfer of bits across the company backbone for a mission critical financial application. The administrator notices that the network throughput appears lower than the bandwidth expected. Which three factors could influence the differences in throughput? (Choose three.)

• the amount of traffic that is currently crossing the network

• 
  the sophistication of the encapsulation method applied to the data

• 
  the type of traffic that is crossing the network

• 
  the latency that is created by the number of network devices that the data is crossing

• 
  the bandwidth of the WAN connection to the Internet

Answer explanation

Throughput usually does not match the specified bandwidth of physical links due to multiple factors. These factors include, the amount of traffic, type of traffic, and latency created by the network devices the data has to cross.

What are two characteristics of fiber-optic cable? (Choose two.)

• 
  It typically contains 4 pairs of fiber-optic wires.

• 
  It combines the technique of cancellation, shielding, and twisting to protect data.

• 
  It is more expensive than UTP cabling is.

• 
  It is not affected by EMI or RFI.

• 
  Each pair of cables is wrapped in metallic foil.

Answer explanation

Fiber-optic cabling supports higher bandwidth than UTP for longer distances. Fiber is immune to EMI and RFI, but costs more, requires more skill to install, and requires more safety precautions.

In addition to the cable length, what two factors could interfere with the communication carried over UTP cables? (Choose two.)

• 
  signal modulation technique

• 
  electromagnetic interference

• crosstalk

• size of the network

• • bandwidth

Answer explanation

Copper media is widely used in network communications. However, copper media is limited by distance and signal interference. Data is transmitted on copper cables as electrical pulses. The electrical pulses are susceptible to interference from two sources:

• Electromagnetic interference (EMI) or radio frequency interference (RFI) - EMI and RFI signals can distort and corrupt the data signals being carried by copper media.

• Crosstalk - Crosstalk is a disturbance caused by the electric or magnetic fields of a signal on one wire interfering with the signal in an adjacent wire.

What is the function of the CRC value that is found in the FCS field of a frame?

• to compute the checksum header for the data field in the frame

• to verify the physical address in the frame

• 
  to verify the integrity of the received frame

• to verify the logical address in the frame

Answer explanation

The CRC value in the FCS field of the received frame is compared to the computed CRC value of that frame, in order to verify the integrity of the frame. If the two values do not match, then the frame is discarded.

What is contained in the trailer of a data-link frame?

• data

• • error detection

• • logical address

• 
  physical address

Answer explanation

The trailer in a data-link frame contains error detection information that is pertinent to the frame included in the FCS field. The header contains control information, such as the addressing, while the area that is indicated by the word "data" includes the data, transport layer PDU, and the IP header.

A network team is comparing physical WAN topologies for connecting remote sites to a headquarters building. Which topology provides high availability and connects some, but not all, remote sites?

• 
  partial mesh

• 
  point-to-point

• 
  hub and spoke

• mesh

Answer explanation

Partial mesh topologies provide high availability by interconnecting multiple remote sites, but do not require a connection between all remote sites. A mesh topology requires point-to-point links with every system being connected to every other system. A point-to-point topology is where each device is connected to one other device. A hub and spoke uses a central device in a star topology that connects to other point-to-point devices.

Which statement describes an extended star topology?

• 
  Each end system is connected to its respective neighbor via an intermediate device.

• 
  End devices are connected together by a bus and each bus connects to a central intermediate device.

• 
  All end and intermediate devices are connected in a chain to each other.

• 
  End devices connect to a central intermediate device, which in turn connects to other central intermediate devices.

Answer explanation

In an extended star topology, central intermediate devices interconnect other star topologies.

What is a characteristic of the LLC sublayer?

• • 
    It places information in the frame allowing multiple Layer 3 protocols to use the same network interface and media.

• 
  It provides the logical addressing required that identifies the device.

• 
  It provides delimitation of data according to the physical signaling requirements of the medium.

• 
  It defines software processes that provide services to the physical layer.

Answer explanation

The Logical Link Control (LLC) defines the software processes that provide services to the network layer protocols. The information is placed by LLC in the frame and identifies which network layer protocol is being used for the frame. This information allows multiple Layer 3 protocols, such as IPv4 and IPv6, to utilize the same network interface and media.

During the encapsulation process, what occurs at the data link layer for a PC connected to an Ethernet network?

• The process port number is added.

• An IP address is added.

• The physical address is added.

• 
  The logical address is added.

Answer explanation

The Ethernet frame includes the source and destination physical address. The trailer includes a CRC value in the Frame Check Sequence field to allow the receiving device to determine if the frame has been changed (has errors) during the transmission.

What type of communication rule would best describe CSMA/CD?

• access method

• message encapsulation

• message encoding

• flow control

Answer explanation

Carrier sense multiple access collision detection (CSMA/CD) is the access method used with Ethernet. The access method rule of communication dictates how a network device is able to place a signal on the carrier. CSMA/CD dictates those rules on an Ethernet network and CSMA/CA dictates those rules on an 802.11 wireless LAN.