Cisco Networking Chapter 5

Front 1

Protocol Data Units (PDUs)

Back 1

When messages are sent between hosts on an "ethernet" network, the host formats the message into the frame layout specified by the standards.

Front 2

What layer does ethernet operate in?

Back 2

Ethernet operates in the data link layer (layer 2) and the physical layer (layer 1).

Front 3

What bandwidth speeds does ethernet support?

Back 3

10mb/S to 100,000 mb/S (100 gb/s)

Front 4

What sub layers does ethernet rely on?

Back 4

LLC (Logical Link Control) - Handles the communication between the upper and lower layers. This is typically between the networking software and the device hardware. The LLC sub layer takes the network protocol Data, which is typically an IP4 packet, and adds control information to help deliver the packet to the destination node.

MAC sub layers - constitutes the lower sub layer of the data link layer. MAC is implemented by hardware, typically in the NIC.

Front 5

What are the 2 responsibilities of the ethernet sub layer?

Back 5

Data encapsulation

Media access control

Front 6

3 primary functions of data encapsulation

Back 6

Frame delimiting

Addressing

Error detection

Front 7

Ethernet relies on 2 sub layers of the data link

Back 7

LLC (Logical Link control) sub layer

MAC sub layer

Front 8

What is the LLC sub layer?

Back 8

Handles communication between upper and lower layers (network software and device hardware)

The LLC sub layer is used to communicate with he upper layers of the application and transition the packet to the lower layers for delivery.

Front 9

2 responsibilities of MAC Sub layer

Back 9

Data encapsulation

Media access control

Front 10

Carrier sense multiple access (CSMA)

Back 10

CSMA/CD (Collision detection)

CSMA/CA (Collision avoidance)

Front 11

How many bits in a MAC address?

Back 11

48 bit (6 bytes)

12 hexadecimal digits (4 bits per digit)

Front 12

OUI (Organisationally unique identifier)

Back 12

The IEEE assigns the vendor 3 byte (24 bit) code called OUI

Front 13

What is a MAC address also referred to as?

Back 13

Burned in address (BIA)

Because, historically, this address is burned into the ROOM on the NIC

Front 14

2 styles of ethernet framing

Back 14

IEEE 802.3 ethernet standard

DIX ethernet standard (ethernet II)

Front 15

Size of ethernet frame

Back 15

Minimum frame 64 bytes

Maximum frame 1518 bytes

Front 16

Ethernet frame collisions

Back 16

If any frame is less than 64 bytes in length, it is considered a "collision fragment" or "runt frame"

Front 17

Primary fields in an ethernet frame

Back 17

Preamble (7 bytes)

Start of frame delimiter (1 byte)

Destination address (6 bytes)

Source address (6 bytes)

Length (2 bytes)

802.2 header information and data (46-1500 bytes)

Frame check sequence (4 bytes)

Front 18

What does the preamble field do in ethernet field?

Back 18

Notifies destination to get ready for a new frame

Front 19

What does the start of frame delimiter field in an ethernet frame do?

Back 19

Synchronises sending and receiving frame for delivery

Front 20

How many bytes in a source MAC address?

Back 20

6 bytes (48 bit)

Front 21

What does the frame check sequence field in an ethernet frame do?

Back 21

Detects errors in an ethernet frame. It uses cycle redundancy check (CRC) to look for errors. If calculations match, no error occurred. Calculations that do not match means data has been changed and frame is dropped.

Front 22

MAC address of broadcast

Back 22

FF-FF-FF-FF-FF-FF

Front 23

2 protocols that used broadcast

Back 23

DHCP

ARP

Front 24

Range of multicast addresses

Back 24

224.0.0.0 to 239.255.255.255

Front 25

What would a multicast address be used in?

Back 25

Online gaming

Video conferencing

Front 26

First 6 digits in a multicast MAC address

Back 26

01-00-5E

Front 27

What does ARP stand for?

Back 27

Address resolution protocol

Front 28

What layer is ARP?

Back 28

Layer 2

Front 29

2 functions of ARP

Back 29

Resolve IPv4 addresses to MAC addresses

Maintain a table of mapping

Front 30

Where is ARP table stored

Back 30

RAM of device

Front 31

What is ARP spoofing?

Back 31

Technique used by an attacker to inject the wrong MAC address association into a network by issuing fake ARP replies

Front 32

What is A MAC address also referred to as?

Back 32

Content addressable memory (CAM)

Front 33

2 methods of frame forwarding?

Back 33

Store and forward forwarding

Cut through forwarding

Front 34

What does store and forward switching do in frame forwarding?

Back 34

Receives entire frame, then computes CRC (Cyclone redundancy check). If CRC us valid, the frame is forwarded. Store and forward switching is required for Quality of Service (QoS).

Front 35

What does cut through switching do in frame forwarding?

Back 35

Forwards the frame before it is entirely received. The destination address must be read before frame is forwarded. The switch does not perform any error checking on the frame. This method is faster but it will forward corrupt frames throughout the network. The destination NIC eventually discards the corrupt frame.

Front 36

2 variations of cut through switching

Back 36

Fast forward switching (no checks whatsoever)

Fragment free switching (checks first 64 bytes of frame

Front 37

2 methods of memory buffering

Back 37

Port based memory

Shared memory

Front 38

What is CEF?

Back 38

Cisco express forwarding.

CEF decouples the usual strict independence between layer 2 and layer 3 decision making to make forwarding faster.

Front 39

2 components of CEF (cisco express forwarding) operations

Back 39

Forwarding information base

Adjencency tables