Chapter 9 Flashcards
(17 cards)
Name the two data link sublayers, and list their purposes.
- Logical Link Control (LLC): Handles the communication between the upper layers and the lower layers, typically hardware.
- MAC: The Ethernet MAC sublayer has the following responsibilities:
■ Data encapsulation
■ Media access control
■ Addressing
Which of the following describes a limitation of legacy Ethernet technologies?
A. Poor scalability
B. Expensive media
C. No collisions
D. Frame format incompatible with current Ethernet
A. Poor scalability
Which field of an Ethernet frame is used for error detection?
A. Type
B. Preamble
C. Frame Check Sequence
D. Destination MAC Address
C. Frame Check Sequence. The FCS (4 bytes in length) field is used to detect errors in a frame.
How many bits are in an Ethernet MAC address?
A. 12
B. 32
C. 48
D. 256
C. An Ethernet MAC address is a 48-bit binary value expressed as 12 hexadecimal digits.
Why are Layer 2 MAC addresses necessary?
An Ethernet MAC address is used to transport the frame across the local media
Which of the following addresses is used as a destination address for an Ethernet broadcast frame?
A. 0.0.0.0
B. 255.255.255.255
C. FF-FF-FF-FF-FF-FF
D. 0C-FA-94-24-EF-00
C. The Ethernet broadcast MAC address is FF-FF-FF-FF-FF-FF. Frames with this destination address are delivered to and processed by all the devices on that LAN segment.
What is the purpose of the jam signal in CSMA/CD?
A. To allow the media to recover
B. To make sure that all sending nodes see the collision
C. To notify other nodes that a node is about to send
D. To identify the length of a frame
B. The jam signal in CSMA/CD makes sure that all sending nodes see the collision.
Describe an Ethernet collision domain.
The group of connected devices that can cause collisions to occur with each other is known as a collision domain. Collision domains occur at Layer 1 of the networking reference model.
What Ethernet characteristic is shared by historic Ethernet and legacy Ethernet?
A. Same cable type
B. Same segment lengths
C. Same logical topology
D. Same installation cost
C. Historic Ethernet and legacy Ethernet both use logical bus topology.
Which of the following describes a connection to a switch port?
A. Isolates broadcasts
B. Is a separate collision domain
C. Uses the MAC address of the switch port as the destination
D. Regenerates every bit that arrives out every port on the switch
B. Is a separate collision domain
What is the stage of operation of an Ethernet switch that creates MAC table entries?
A. Aging
B. Filtering
C. Flooding
D. Learning
D. Learning. When a frame of data is received from a node, the switch reads the source MAC address and saves the address to the lookup table against the incoming interface. The switch now knows out which interface to forward frames with this address.
If a frame arrives at a switch that contains a source MAC address that is not listed in the MAC table, what process will occur?
A. Aging
B. Filtering
C. Flooding
D. Learning
D. Learning. When a frame of data is received from a node, the switch reads the source MAC address and saves the address to the lookup table against the incoming interface. The switch now knows out which interface to forward frames with this address.
When does a network host need to broadcast an ARP request?
When a host has a packet to send to an IP address that does not have a map in the ARP cache.
If a frame arrives at a switch that contains a destination MAC address that is not listed in the MAC table, what process will occur?
A. Aging
B. Filtering
C. Flooding
D. Learning
C. Flooding. When the switch does not have a destination MAC address in its lookup table, it sends (floods) the frame out all interfaces except the one on which the frame arrived.
Why are higher-speed Ethernet implementations more susceptible to noise?
A. More collisions
B. Shorter bit times
C. Full-duplex operation
D. UTP cables are required instead of fiber
B. Timing can be more easily distorted with the shorter bit times.
Discuss why Ethernet has maintained the same frame format and what might have resulted from changing the frame format.
(Can vary.) With the same frame format, different implementations of Ethernet (PHY) maintain compatibility. Changing the frame format would have resulted in different “Ethernets” that were not compatible.
Discuss the reasons why using LAN switches improves the security of a network.
(Can vary.) The primary reason is that the frames are not sent to every device. If a device receives a frame, it can be examined to obtain the sensitive information.
