LAN Switching Fundamentals Flashcards
What is a Broadcast Domain?
A broadcast domain contains all devices that can reach each other at the data link layer (OSI layer 2) by using broadcast.
What is a Collision Domain?
Collection of devices that all share the same medium ie switch or hub.
What are the two major ways that traffic is able to be sent over the same wire with multiple host?
Time Division Multiplexing (Alternates signals from host so each signal has a certain amount of time before the next signal is put on the wire) and Frequency Division Multiplexing (IE Radios)
What is CSMA/CA?
Carrier Sense Multiple Access with Collision Detection
What is it called when on a communication link only one person can talk and then goes quiet while someone else talks and then talks again when it’s their turn?
Half Duplex
What is called when both sides of a communication link are able to talk at the same time?
Full Duplex
What is Carrier Sense?
When a host is listening to a wire to see if it detects 1’ and 0’s on it and if so it must be quiet
If Carrier Sense detects no 0’s or 1’s it must do what before putting 0’s and 1’s on the wire?
Wait a specific amount of time to make sure no one else starts talking first.
What is a MTU?
Maximum Transmission Unit, the maximum size of any data unit.
What is it when all devices have access to a wire and anyone can talk?
Multiple Access
What happens if collision is detected on a wire?
The transmission is stopped wherever it is and then the time to wait before putting a signal on the wire is widen a bit before trying again and will repeat this process 16 times before dropping the signal all together.
What is the structure of a DIX Ethernet Frame?
Bonus how many bytes for each field?
Preamble(8) | Destination Address(6) | Source Address(6) | Type(2) | Data (or Padding)(46 - 1500) | FCS(4)
What is the Preamble?
A constant pattern at the beginning of an ethernet frame that acts as a wake up call saying “Hey here come an ethernet packet”
What is the structure of a IEEE 802.3 Ethernet Frame?
Bonus how many bytes for each field?
Preamble(7) | Start of Frame Delimiter (1) | Destination Address (6) | Source Address (6) | Length(2) | 802.2 Header + Data (46-1500) | FCS (4)
How many bits are in a MAC Address?
48 bits
What are the first 24 bits called?
The Organizationally Unique Identifier
The last 24 bits of a MAC Address on a NIC Card are?
Unique within the organization.
In the first byte (1E Below) of a MAC Address the first two bits are very important, what does each bit represent?
1E:4B:2A:3A:BB:CA
Bit 1: Individual or Group bit.
If set to a 0 it’s an individual MAC Address. If it’s set to 1 it’s a group MAC Address , ie MAC broadcast FF:FF:FF:FF:FF:FF
Bit 2: The Global or Local bit
If set to 0 it’s a global address and if it’s set to 1 it’s a local address. The bit that is flipped during EUI-64
What is a Straight-Through Cable and when is it used?
Where pin 1 on one side goes to pin 1 on the other side and the same goes for all 8 pins.
Used when connecting devices that are at different OSI Model Layers
What is a Cross-Over Cable and when is it used?
Pin 1 goes to Pin 3
Pin 2 goes to Pin 6
Rest of the pins match up
Used when connecting devices at similar OSI Model Layers
What is a Rolled Cabled and when is it used?
The pins are reversed, pin 1 on one side goes to pin 8 on the other and you do that all the way down.
Used when connecting devices to console ports, not meant for ethernet frames.
What is a switch?
Networking device that connects devices together on a computer network by using packet switching to receive, process, and forward data to the destination device. Allows for different speeds on different ports.
How does a switch handle collision?
Separates the collision domains. Each port has memory for a receive and transport buffer so that if frames come in at the same time the port waits until it’s turn and then either sends or receives that frames.
What layer does a switch operate at?
The data link layer (2)
What is a MAC Address Table and how is it used?
Stored addresses within a switch that are learned from plugging the device into it for the first time. It uses this to know where to forward traffic to.
What is the amount of time a Cisco switch will wait before forgetting a MAC Address after not seeing it?
5 minutes.
The forwarding of frames is based off of the what?
The Destination MAC Address
What is the start up process switches and routers generally go through?
- Discover device hardware
- Find and load IOS Image
- Find and load config file
By default where is the IOS stored?
In flash memory.
By defualt where is the Start-up Config File stored?
In NVRAM memory
Which two memory typed retain their information even if the system is powered off?
Flash and NVRAM (Non-Volatile Random Access Memory)
Where is the IOS and Start-up config copied to when the device is running?
To the DRAM