Cisco Network Fundamentals - Chapter 9

Front 1

Name the two data link sublayers, and their purposes.

Back 1

LLC, Logical Link Control, handles the communication between the upper layers and the lower layers, typically hardware

MAC - The ethernet MAC is responsible for data encapsulation, media access control, addressing

Front 2

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

Back 2

a) poor scalability

Front 3

Which field of an Ethernet frame is used for error detection?

Type, preamble, frame check sequence, or destination MAC address

Back 3

c) Check frame sequence. The FCS (4 bytes in length) field is used to detect errors in a frame

Front 4

How many bits are in an Ethernet MAC address?

Back 4

48-bits, expressed as 12 hexidecimal digits

Front 5

Why are Layer 2 MAC addresses necessary?

Back 5

To transport the frame across the local media

Front 6

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

Back 6

c) the ethernet broadcast MAC address is FF-FF-FF-FF-FF-FF

Front 7

What is the purpose of a jam signal?

Back 7

b) the jam signal is CSMA/CD make sure that all sending nodes see the collision

Front 8

Describe an Ethernet collision domain.

Back 8

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 OSI.

Front 9

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

Back 9

b) is a separate collision domain

Front 10

What is the only layer that has two sublayers?

Back 10

The data link layer

Front 11

Switches switch on __________________, not IP

Back 11

MAC addresses

Front 12

__________ is physical, __________ is logical

Back 12

MAC and IP

Front 13

Is it better or worse to have more collision domains?

Back 13

It's actually better (trick question!)...you have less chances of collisions that way

Front 14

MAC tables are built on destination or source?

Back 14

Source

Front 15

ARP stands for?

Back 15

Address Resolution Protocol

Front 16

Ethernet sits on what layer?

Back 16

Layer 2 (the data link layer)...also layer 1 (physical)

Front 17

The Ethernet address is technically the ________________ address, not the IP

Back 17

MAC address

Front 18

What is the length limit for untwisting wires when making a CAT5 cable?

Back 18

1/2 inch--no more than that

Front 19

What si the major problem with using CSMA/CD?

Back 19

Network performance can decrease because of collisions (which are normal)

Front 20

Where does the IEEE 802.2 standard reside?

Back 20

data link layer, LLC sublayer

Hint: IEEE 802.2 is another name for ethernet

Front 21

Convert the binary number 11111010 to hexidecimal

Back 21

FA

Front 22

Which sublayer performs identification of network layer protocols?

Back 22

The LLC, upper data link layer

Front 23

What is interframe spacing and how is it measured?

Back 23

The Ethernet standards require a minimum spacing between two non-colliding frames (96 bit times). This gives the media time to stabilize after the transmission of the previous frame and time for the devices to process the frame. It is measured from the last bit of the FCS field of one frame to the first bit of the preamble of the next frame.

Front 24

Which plex/modes have no collisions?

Back 24

Simplex and full duplex

Front 25

How do hosts with traffic to deal with respond after a backoff period has expired?

Back 25

The hosts return to a listen-before-transmit mode

Front 26

What is a major advantage of using switches over hubs in a network?

Back 26

Switches can control the flow of data by isolating each port and sending a frame only to it's proper destination, rather than flood everywhere. By reducing the number of deices receiving frames it minimized collisions and therefore increases thoroughput.

Front 27

What is primarily used for networking today (cables)?

Back 27

Copper UTP and fiber optic

Front 28

What is the primary purpose of ARP?

Back 28

Resolves/links IP addresses to corresponding MAC addresses

Front 29

LLC sublayer is implemented in hardware or software?

Back 29

Software

Front 30

The MAC sublayer is implemented by software or hardware?

Back 30

Hardware, typically the computer's NIC

Front 31

IEEE 802.2 describes which sublayer function, LLC or MAC?

Back 31

LLC.

802.3 is the MAC sublayer.

Front 32

An ethernet frame contains?

Back 32

A preamble, start frame delimiter, destination address, source address, length/type, 802.2 header and data, frame check sequence

Front 33

The decimal number 8, which is 1000 in binary, is represented how in hex?

Back 33

8

Front 34

The decimal number 10, which is 1010 in binary, is represented how in hex?

Back 34

A

Front 35

Hubs do or do not break up collision domains?

Back 35

do NOT

Front 36

What is the difference between 568A and 568B?

Back 36

The only difference between 568A and 568B is that pairs 2 and 3 (orange and green) are swapped.

Front 37

What is crosstalk?

Back 37

Crosstalk is the "bleeding" of signals from one pair in a cable onto another pair through induction (wires need not make contact because signals are transferred magnetically). Crosstalk is an unwanted effect that can cause slow data transfer, or completely inhibit the transfer of data signals. Crosstalk is minimized by the twisting of the pairs in the cable. Fiber Optic cable is the only cable medium that is 100% immune to the effects of crosstalk or EMI.

Front 38

What is EMI?

Back 38

Similar to crosstalk, EMI is an unwanted signal that is induced into the cable. The difference is that EMI typically comes from a source that is external to the cable, such as an electrical cable or device.

Front 39

What is attenuation?

Back 39

Attenuation is the loss of signal over the length of a network link due to the resistance of the wire plus other electrical factors that cause additional resistance (impedance and capacitance for example). A longer cable length, poor connections, bad insulation, a high level of crosstalk, or EMI can all increase attenuation. For each category of cable, the TIA-568B standard specifies the maximum amount of attenuation that is acceptable in a network link.