Chapter 3: Ethernet Basics Flashcards
Define: L2 Ethernet Frame - Destination Address and Source Address Fields
The MAC address of the frame’s recipient and the Mac address of the sending system.
Define: L2 Ethernet Frame - Type Field
Helps the receiving system interpret the frame contents at a very basic level, such as what version of IP addressing is used.
What is contained in the Ethernet Frame data field?
Contains whatever payload the frame carries.
Define: L2 Ethernet Frame - Pad
Brings the data up to the minimum 64 bytes required for an Ethernet frame.
Define: L2 Ethernet Frame - Frame Check Sequence (FCS)
The cyclic redundancy check (CRC) value used by the receiving system to check the data for errors.
Define: L2 Ethernet Frame - Preamble
A 7-byte series of alternating ones and zeroes followed by a 1-byte start frame delimiter or an 8-byte series of ones and zeroes, that precedes a frame.
What is the purpose of a Ethernet frame preamble?
It gives a receiving NIC time to realize a frame is coming and to know where the frame starts.
Breakdown the parts of 10BASE-T
10: Refers to the speed. In this case 10 Mbps.
BASE: Refers to the signaling type, baseband.
T: Refers to the type of cable used. In this case twisted pair.
Define: Baseband
Means that the cable carries only one signal.
What pins on an RJ-45 connector are used by 10BASE-T devices?
Pins 1 and 2 send data, and pins 3 and 6 receive data.
What is the wire termination order for 568A twisted pair Ethernet cabling?
From left to right:
1. Green/White
2. Green
3. Orange/White
4. Blue
5. Blue/White
6. Orange
7. Brown/White
8. Brown
Remember “GO”
What is the wire termination order for 568B twisted pair Ethernet cabling?
From left to right:
1. Orange/White
2. Orange
3. Green/White
4. Blue
5. Blue/White
6. Green
7. Brown/White
8. Brown
10BASE-T Summary:
Speed
Distance
Node Limit
Cable Type
Speed: 10 Mbps
Distance: 100 m
Node Limit: No more than 1024 nodes per hub
Cable Type: Cat 3 or better UTP
What is a media converter device?
A device used to interconnect different Ethernet types (ie. twisted pair and fiber-optic).
Define: Carrier-Sense Multiple Access with Collision Detection (CSMA/CD)
A system used on Ethernet networks to determine which computer should use a shared cable at a given moment. It is disabled in modern full-duplex networks.
Define: Collision Domain
A group of nodes that have the capability of sending frames at the same time as each other, resulting in collisions.
Define: Switches
A Layer 2 device that filters network traffic by using MAC addresses and port mapping. Each port on a switch is its own collision domain. Switches send all broadcast messages to all the ports (except the port on where it came from). Switched networks are broadcast domains.
How do you connect older technology switches?
Either by an uplink port or a crossover cable.
How do you connect two switches using an uplink port?
You use a straight-through cable inserted into the uplink port of one switch with the other end inserted into a regular port on the other switch.
Modern switches do not have a dedicated uplink port.
How do you connect two switches using a crossover cable?
Insert the crossover cable to a regular port on each switch. The crossover cable allows the switches to hear each other.
Define: Crossover Cable
A twisted pair cable where one end is terminated with 568A and the other is terminated with 568B.
Define: Auto-Medium-Dependent Interface Crossover (MDI-X)
The technical term for an uplink port and the auto-sensing features of ports in modern switches.
What does Spanning Tree Protocol (STP) do, and what special type of frame does it use for communication between switches?
STP eliminates the problem of accidental switching loops by electing one switch as the root bridge. Bridge protocol data units (BPDUs) are the frames used to communicate between switches.
What protocol replaced STP?
Rapid Spanning Tree Protocol (RSTP)
