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Flashcards in Ethernet Deck (31):
1

Original designer of Ethernet

Robert Metcalfe and Xerox

2

Which layer is Ethernet

Layer 2 of OSI model (MAC addressing), Layer 1 OSI model (signaling)

3

Data encapsulation primary functions

Framing: group of bits making up a frame
Addressing
Error detection: CRC

4

Ethernet cables used today

UTP Copper and optical fiber

5

First versions of Ethernet used...

Coax cable

6

10BASE5

aka Thicknet; used a thick coaxial; cabling distance up to 500 m

7

10BASE2

aka Thinnet; smaller in diameter and more flexible than Thicknet

8

Hubs...

Take a group of nodes and allow the network to see them as a single unit; only one station could transmit at a time (half-duplex communication)

9

Switches...

only send frame only to its proper destination port (if it's known) = full-duplex communication

10

Gigabit Ethernet

used to describe Ethernet implementations that provide bandwidth of 1000 Mbps (1 Gbps) or greater

11

Characteristic(s) of Ethernet MAC addresses

a 48-bit or 64-bit binary value expressed as 12 hexadecimal digits; use ipconfig/all
01-23-45-67-89-AB

12

Special value of Multicast addresses

01-00-5E

13

Detecting collisions on devices

all devices can detect an increase in the amplitude of the signal above the normal level causing a JAM SIGNAL

14

Response to JAM signal

invokes a backoff algorithm to all devices to stop transmitting for a random amount of time, allowing collisions to subside

15

Preamble

situation where a collision has not occurred during half duplex mode and the sending device transmits 64 bits of synchronization

16

Asynchronous communication

Ethernet with speeds of 10 Mbps and slower; required timing info to synchronize the receive circuit to the incoming data and then discard the 8 bytes.

17

Synchronous communication

timing info not required

18

In order for CSMA/CD to operate....

the sending device must become aware of a collision before it has completed transmission of a minimum-sized frame

19

Slot time

longer than the theoretical amount of time required to travel between the furthest points of the collision domain, collide with another transmission at the last possible instant, and then have the collision fragments return to the sending station and be detected

20

most commonly observed data for a jam signal is..

a repeating 1, 0, 1, 0 pattern, the same as the Preamble

21

Four data rates currently defined for operation over optical fiber and TP:

10BASE5, 10BASE2, 10BASE-T (using cat3/cat5 UTP), 100Mbps - Fast Ethernet

22

Transmission pairs of UTP

1,2 = transmitting
3,6 = receiving

23

1000BASE-T characteristics

Provides full-duplex transmission using all four pairs in Category 5 or later UTP cable

24

Latency

time it takes a signal to reach all destinations on the media. Increasing the length of the media increases latency

25

Collision domain

any part of the network where packets from two or more nodes can interfere with each other

26

Switch increases throughput of network by...

A dedicated bandwidth to each port
Collision-free environment
Full-duplex operation

27

Ethernet LAN switch five basic functions:

Learning: Switch examines source MAC address
Aging: MAC entries are timestamped
Flooding: floods all ports if destination MAC address is unknown
Selective Forwarding
Filtering: does not forward a frame to the same port in which it arrived

28

ARP protocol

Resolves IPv4 addresses to MAC addresses
Maintains a cache of mappings

29

ARP process

1. When ARP receives a request to map an IPv4 address to a MAC address. it looks for the cached ARP address in its table.
2. It sends a broadcast (ARP request) to discover the MAC address of the destination device on the local network

30

Proxy ARP

useful for when a host might send an ARP request seeking to map an IPv4 address outside of the range of the local network

ARP cache of requesting device will contain the MAC address associated with the IPv4 address of the gateway.

31

ARP spoofing

A technique used by an attacker to inject the wrong MAC address association into a network by issuing fake ARP requests.