Fundamentals of Ethernet LANs

Question 1

Name the two types of LANs?

Answer 1

Ethernet LANs and wireless LANs

Question 2

Ethernet LANs are often known as?

Answer 2

wired LANs - due to the fact they use cables for the links between nodes.

Question 3

How do wireless LANs connect?

Answer 3

Using radio waves

Question 4

What does the term Ethernet refer to?

Answer 4

a family of LAN standards that together define the physical and data link layers of teh world’s most popular wired LAN technology.

Question 5

What is a Ethernet LAN switch

Answer 5

provides many physical ports into which cables can be connected

Question 6

Define Ethernet cables?

Answer 6

cables which is a general reference to any cable that conforms to any of several Ethernet standards.

Question 7

What does SOHO mean?

Answer 7

Small Office/Home Office

Question 8

True of False

Does the term Ethernet refer to an entire family of standards

Answer 8

True

Ethernet standards come from the IEEE and include the number 802.3 as the begining part of the standard name.

Question 9

What does UTP stand for?

Answer 9

Unshielded Twisted Pair

Question 10

The formal name begins with 802.3 followed by some suffix letter,

What is the suffix letter for cabling or fiber?

Answer 10

For UTP - suffix T

For Fiber - suffix X

Question 11

Types of Ethernet

Answer 11

Question 12

What is a Ethernet LAN

Answer 12

It is a combination of user devices, LAN switches, and different kinds of cabling.

Question 13

What are three of the most commonly used Ethernet standards

Answer 13

1. 10BASE-T (Ethernet)
2. 100BASE-T (Fast Ethernet or FE)
3. 1000BASE-T (Gigabit Ethernet, or GE)

Question 14

What is a encoding scheme

Answer 14

with an encoding scheme, the transmitting node changes the electrical signal over time, while the other node, the receiver, using the same rules, interprets those changes as either 0s or 1s.

Question 15

What is EMI

Answer 15

EMI stands for (electromagnetic interference) - which happens when electrical current passes over any wire.

Question 16

EMI between wire pairs in the same cable is called

Answer 16

Crosstalk

Question 17

Define the term Ethernet link

Answer 17

Ethernet link refers to any physical cable between two Ethernet nodes.

Question 18

True or False

Does 10BASE-T and 100BASE-T standards require two pairs of wires, while the 1000BASE-T standard requires four pairs

Answer 18

True

Question 19

The RJ-45 connector has eight physical locations into which the eight wires in the cable can be inserted, called

Answer 19

pin positions or pins

Question 20

Using One Pair for EAch Transmission Direction with 10 and 100 Mbps Ethernet

Answer 20

Question 21

Understanding the wiring of the cable

For NIC

For Switches

Ethernet Straight-Through Cable Concept

Answer 21

Ethernet NIC transmitters use the pair connected to pins 1 and 2; the NIC receivers use a pair of wires at pin positions 3 and 6.

LAN Switches receivers use the wire pair at pins 1 and 2, and their transmitters use the wire pair at pins 3 and 6

Question 22

What is a crossover cable

Answer 22

The crossover cable pinout crosses the pair at the transmit pins on each device to the receive pins on the opposite device

Question 23

What are the differences between crossover and straight-through cables

Answer 23

Crossover cable: Are when the endpoints transmit on the same pin pair

Straight-through cable: Are if the endpoints transmit on different pin pairs

Question 24

10BASE-T and 100BASE-T Pin Pairs Used

Answer 24

Question 25

How does 1000BASE-T (Gigabit Ethernet) differ from 10BASE-T and 100BASE-T as far as the cabling and pinouts

Answer 25

1. 1000BASE-T requires four wire pairs, 2. It uses more advanced electronics that allow both ends to transmit and receive simultaneously on each wire pair.

Question 26

How does Gigabit Ethernet crossover cable cross

Answer 26

The pairs at pins 1,2 and 3,6) and (the pair at pins 4,5 with the pair at pins 7,8)

Question 27

IEEE 802.3 Ethernet Header and Trailer Fields

Answer 27

Question 28

Is this statement True or False The IEEE 802.3 specification limits the data portion of the 802.3 frame to a minimum of 46 and a maximum of 1500 bytes.

Answer 28

True

Question 29

Define term MTU

Answer 29

MTU mean Maximum Transmission unit (MTU) - it defines the maximum Layer 3 packet that can be sent over a medium

Question 30

True or False 1500 bytes is the largest IP MTU allowed over an Ethernet

Answer 30

True

Question 31

True or False Ethernet addresses, also called Media Access Control (MAC) addresses, are 6-byte-long (48-bit-long) binary numbers

Answer 31

True

Question 32

Define the term unicast

Answer 32

the term unicast is simply a formal way to refer to the fact that the address represents one interface to the Ethernet LAN

Question 33

What does OUI mean

Answer 33

Organizationally unique identifier

Question 34

Explain the OUI

Answer 34

The IEEE assign the manufacturer a universally unique 3-byte code and the manufacturer assigns a unique value for the last 3-bytes

Question 35

True or False The IEEE also calls these universal MAC addresses global MAC addresses

Answer 35

True

Question 36

Show the structure of the unicast MAC address, with OUI

Answer 36

Question 37

True or False The term burned-in address (BIA) refers to the idea that a permanent MAC address has been encoded (burned-into) the ROM chip on the NIC

Answer 37

True

Question 38

The IEEE defines two general catagories for group addresses for Ethernet

Answer 38

1. **Broadcast address**: Frames sent to this address should be delivered to all devices on the Ethernet LAN. It has a value of FFFF.FFFF.FFFF 2. **Multicast addresses**: Frames sent to a multicast Ethernet address will be copied and forwarded to a subset of the devices on the LAN that volunteers to receive frames sent to a specific multicast address.

Question 39

LAN MAC Address Terminology and Features

Answer 39

Question 40

True or False The Ethernet Frame Check Sequence (FCS) field in the Ethernet trailer -- the only field in the Ethernet trailer---gives teh receiving node a way to compare results with the sender, to discover whether errors occured in the frame.

Answer 40

True

Question 41

Half duplex

Answer 41

The device must wait to send if it is currently receiving a frame; in other words, it cannot send and receive at the same time.

Question 42

Full duplex

Answer 42

The device does not have to wait before sending: it can send and receive at the same time.

Question 43

True or False Node that use half duplex logic actually use a relatively well-known algorithm called carrier sense multiple access with collision detection (CSMA/CD)

Answer 43

True

Question 44

CSMA/CD covers these cases

Answer 44

Step 1. - A device with a frame to send listens until the Ethernet is not busy Step 2. - When the Ethernet is not busy, the sender begins sending the frame. Step 3. - The sender listens while sending to discover whether a collision occurs; collisions might be caused by many reason, including unfortunate timing. If a collision occurs, all currently sending nodes do the following: a. They send a jamming signal that tells all nodes that a collision happened. b. They independently choose a random time to wait before trying again, to avoid unfortunate timing c. The next attempt starts again at Step 1

Question 45

True or False For all links between PCs and switches, or between switches, use full duplex. However, for any links connected to a LAN hub, the connected LAN switch and NIC port should use half-duplex

Answer 45

True

Question 46

True or False For all links between PCs and switches, or between switches, use full duplex. For link connected to LAN hub, the connected LAN switch and NIC port should use half-duplex

Answer 46

True