Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
69 Cards in this Set
- Front
- Back
|
Which of the following answers is most accurate about the cabling of a typical modern Ethernet LAN?
a. Connect each device in series using coaxial cabling b. Connect each device in series using UTP cabling c. Connect each devices to a centralized LAN hub using UTP cabling d. Connect each device to a centralized LAN switch using UTP cabling. |
d. Connect each device to a centralized LAN switch using UTP cabling.
|
|
|
Which of the following is true about the cabling of a 10BASE2 Ethernet LAN?
a. Connect each device in series using coaxial cabling b. Connect each device in series using UTP cabling c. Connect each devices to a centralized LAN hub using UTP cabling d. Connect each device to a centralized LAN switch using UTP cabling. |
a. Connect each device in series using coaxial cabling
|
|
|
Which of the following is true about Ethernet crossover cables?
a. Pins 1 and 2 are reversed on the other end of the cable. b. Pins 1 and 2 on one end of the cable connect to pins 3 and 6 on the other end of the cable. c. Pins 1 and 2 on one end of the cable connect to pins 3 and 4 on the other end of the cable d. The cable can be up to 1000 meters long to cross over between buildings. |
b. Pins 1 and 2 on one end of the cable connect to pins 3 and 6 on the other end of the cable.
|
|
|
Each answer lists two types of devices used in 100BASE-TX network. If these devices were connected with UTP Ethernet cables, which pairs of devices would require a straight-through cable?
a. PC and router b. PC and switch c. Hub and switch d. Router and hub e.Wireless access point Ethernet ports |
b,d,e, Routers, Routers, wireless access point Ethernet ports, and PC NICs all send using pins 1 and 2, whereas hubs and switches send using pins 3 and 6. Straight-though cables are used when connecting devices that use the opposite pairs of pins to transmit data.
|
|
|
Which of the following is true about CSMA/CD algorithm?
a. The algorithm never allows collisions to occur. b. Collisions can happen, but the algorithm defines how the computers should notice a collision and how to recover c. The algorithm works with only two devices on the same Ethernet. d. None of the answers is correct. |
b. Collisions can happen, but the algorithm defines how the computers should notice a collision and how to recover
|
|
|
Which of the following is a collision domain?
a. All devices connected to an Ethernet hub b. All devices connected to an Ethernet switch c. Two PCs, with one cabled to a router Ethernet port with a crossover cable and the other PC cabled to another router Ethernet port with a crossover cable d. None of the other answers is correct. |
c. Two PCs, with one cabled to a router Ethernet port with a crossover cable and the other PC cabled to another router Ethernet port with a crossover cable
|
|
|
Which of the following describe a shortcoming of using hobs that is improved by instead of using switches?
a. Hubs create a single electrical bus to which all devices connect, causing the devices to share the bandwidth b. Hubs limit the maximum cable length of individual cables (relative to switches) c. Hubs allow collisions to occur when two attached devices send data at the same time. d. Hubs restrict the number of physical ports to at most eight. |
a. Hubs create a single electrical bus to which all devices connect, causing the devices to share the bandwidth
c. Hubs allow collisions to occur when two attached devices send data at the same time. |
|
|
Which of the following terms describe Ethernet addresses that can be used to communicate with more than one device at a time?
a. Burned-in address b. Unicast address c. Broadcast address d. Multicast address |
c. Broadcast address
d. Multicast address |
|
|
Which of the follwoing is one of the functions of OSI Layer 2 protocols?
a. Framing b. Delivery of bits from one device to another c. Error recovery d. Defining the size and shape of Ethernet cards |
a. Framing
|
|
|
Which of the following are true about the format of Ethernet addresses?
a. Each manufacturer puts a unique code into the first 2 bytes of the address. b. Each manufacturer puts a unique code into the first 3 bytes of the address. c. Each manufacture puts a unique code into the first half of the address. d. The part of the address that holds this manufacturer's code is called the MAC e. The part of the address that holds this manufacturer's code is called the OUI |
b. Each manufacturer puts a unique code into the first 3 bytes of the address.
c. Each manufacture puts a unique code into the first half of the address. e. The part of the address that holds this manufacturer's code is called the OUI |
|
|
Which of the following is true about the Ethernet FCS field?
a. It is used for error recovery b. It is 2 bytes long c. It resides in the Ethernet trailer, not the Ethernet head d. It is used for encryption |
c. It resides in the Ethernet trailer, not the Ethernet head
|
|
|
Types of Ethernet
What are the specifications of Ethernet? |
Speed: 10 Mbs
Alt Name: 10BASE-T Standard: IEEE 802.3 Type of cable: Copper 100m |
|
|
Types of Ethernet
What are the specifications of Fast Ethernet? |
Speed: 100Mbs
Alt Name: 100BASE-TX Standard: IEEE 802.3u Type of cable: Copper, 100m |
|
|
Types of Ethernet
What are the specifications of Gigabit Ethernet? |
Speed: 1,000Mbs
Alt Name: 1000BASE-LX, 1000BASE-SX Standard: IEEE 802.3z Types of cable: Fiber, 550m SX 5km LX |
|
|
Types of Ethernet
What are the specifications of |
Speed: 1000Mbs
Alt Name: 1000BASE-T Standard: IEEE 802.3ab Types of cable: Copper 100m |
|
|
To build a UTP-based LAN you may need the following components.
|
1. Computers
2. Either a hub or switch 3. UTP cables to connect each PC to the hub or switch. |
|
|
What is CSMA/CD and what is it's function?
|
Carrier sense multiple access with collision detection algorithm. It works like conversation. A device that wants to send a frame waits until the LAN is silent, no frames are currently being sent before before attempting to send an electrical signal.
If a collision still occurs, the devices that caused the collision wait a random amount of time and then try again. |
|
|
How does a repeater work and it's purpose.
|
A repeater is a layer 1 device to extend signals further than 185m. It will clean up the electrical signal and repeat it without interpreting the meaning of the electrical signal.
|
|
|
Why was CSMA/CD created?
|
It was created because collisons could occur on this bus, Ethernet defined the CSMA/CD algorithm, which defined a way to both avoid collisions and take action when collisions occurred.
|
|
|
How many pins does a RJ45 contain?
|
Eight pins that are used in a connector.
|
|
|
What pins does a NIC receive on?
|
A NIC receives on pins 3 and 6
|
|
|
On what pins does a NIC transmit data on?
|
A NIC transmits data on pins 1 and 2
|
|
|
What devices transmit on pins 1,2 and receive on pins 3,6?
|
PC NICs
Routers Wireless Access Point (Ethernet interface) Networked printers (printers that connect directly to the LAN) |
|
|
What devices transmit on pins 3,6 and receive on 1,2?
|
Hubs and switches.
|
|
|
How does a hub transmit data?
|
It does it by repeating the signal to all the available ports, but not where it has originated.
|
|
|
What is CSMA/CD?
|
Carrier sense multiple access with collision detection. It helps prevent collisions and also defines how to act when a collision does occur.
|
|
|
How does carrier sense multiple access with collision detection work?
|
a device with a frame to send listens until the Ethernet is not busy. When it isn't it begins sending the frame. Senders listen to make sure no collisions occur. If collisions occur, the devices that had been sending a frame send a jamming signal to ensure all stations recognize the collision. After jamming is complete, each sender randomizes a timer and waits before trying to resend the collided frame. When timer expires then starts over.
|
|
|
What is a collision domain?
|
defines the set of devices whose frames could collide. ex: a network using a hub risk collisions between the frames that they send. All devices connected to the hub are in the same collision domain.
|
|
|
How do switches operate?
|
Switches intpret the recieved frame and send out to the one port, rather than all 4 ports. If multiple frames need to be sent out on the same port, the switch buffers the frames in memory, sending one at a time and avoiding collisions.
|
|
|
What are some features of switches?
|
If only one device is cabled to each port of a switch, no collisions can occur. Devices connected to a switch have separate bandwidth. Ex: 100 Mbs bandwidth per port.
|
|
|
What is the difference between shared Ethernet and switched Ethernet?
|
Shared Ethernet means that the LAN bandwidth is shared among the devices on the LAN because they must take turns using the LAN because of CSMA/CD. Switched Ethernet supports 100Mbs per port.
|
|
|
Describe full-duplex operation.
|
Full duplex means that Ethernet card can send and receive concurrently. with a switch and one device no collisions can occur. When full-duplex is enabled CSMA/CD is disabled on both ends of the cable. Performance is doubled.
|
|
|
How does Ethernet addressing work?
|
Ethernet LAN addressing identifies either individual devices or groups of devices on a LAN. Each address is 6 bytes long, Written in hexadecimal and separated by periods. Ex: 000.0C12.3456
|
|
|
Describe Uni-cast.
|
Uni-cast Ethernet addresses identify a single LAN card. Computers use uni-cast addresses to identify the sender and receiver of an Ethernet frame.
|
|
|
What is a MAC address?
|
Media access control is a unique unicast address. The first half of the address is is unique to the manufacture it is usually 24 bits. The second half is a number that has never used on another card is 24 bits.
|
|
|
How does the OUI work?
|
organizationally unique identifier is the code, that is assigned to each manufacturer by IEEE. The OUI is 24bits
|
|
|
What makes up the MAC?
|
The OUI 24bits and the 24bits from the manufacture. Together make a BIA burned in address.
|
|
|
BIA stands for?
|
Burned in address. us called UAA or universally administered addresses. They are both unique unicast addresses.
|
|
|
Unicast addresses can be listed under different names?
|
Some common names are LAN addresses, Ethernet addresses, hardware addresses, physical addresses, or MAC addresses.
|
|
|
What is a group address?
|
A group address identifies more than one LAN interface card. The IEEE defines two general categories of group addresses for Ethernet. Broad cast addresses, and multicast addresses.
|
|
|
How does a broadcast address work?
|
The most often used IEEE group MAC addresses, the broadcast, has a value of FFFF.FFFF.FFFF (hex notation). The broadcast address implies that all devices on the LAN should process the frame.
|
|
|
Multicast addresses?
|
Multicast is used to allow a subset of devices on a LAN to communicate. It is used by IP and follow this format: 1001.5ex.xxx, where any value can be used in the last half of the address.
|
|
|
Mac
|
Media access control. 802.3 (etherent) defines the MAC sublayer of IEEE ethernet.
|
|
|
Ethernet address, NIC address, LAN address
|
Other names often used instead of MAC address. These terms describe the 6-byte address of the LAN interface card
|
|
|
Burned-in address
|
The 6-byte address assigned by the vendor making the card.
|
|
|
Unicast address
|
A term for a MAC that represents a single LAN interface.
|
|
|
Broadcast address
|
An address that means "all devices that reside on this LAN right now."
|
|
|
Multicast address
|
On Ethernet, a multicast address implies some subnet of all devices currently on Ethernet LAN.
|
|
|
How does Ethernet framing work?
|
Ethernet framing defines the meanings behind the bits that are transmitted across a network.
|
|
|
Preamble
|
7 bytes. Description - synchronization
|
|
|
Start frame delimiter (SFD)
|
1 byte. Signifies that the next byte begins the destination MAC field
|
|
|
Destination MAC address
|
6 bytes. Identifies the sender of this frame
|
|
|
Source MAC address
|
6 bytes. Identifies the sender of this frame
|
|
|
length
|
2 bytes, Defines the length of the data field of the frame (either length or type is present, but not both)
|
|
|
Type
|
2 bytes,Defines the type of protocol listed inside the frame (either length or type is present, but not both)
|
|
|
Data and Pad
|
46-1500 bytes holds data from a higher layer, typically an L3 PDU (generic) and often a IP packet
|
|
|
Frame check sequence (FCS)
|
4 bytes, provides a method for the receiving NIC to determine if the frame experienced transmission errors.
|
|
|
What elements does framing contain?
|
The preamble 7bytes, the Start frame Delimiter (SFD) 1byte, Destination MAC 6bytes, Source MAC 6bytes, Length 2bytes, type 2bytes, Data and pad 46-1500bytes, Frame check sequence 4bytes.
|
|
|
802.3 frame
|
Maximum of 1500 bytes for layer 3 packets. Maximum transmission unit (MTU) defines layer 3 packet over a medium. Layer 3 packet is inside of Ethernet frame. 1500 is the largest allowed over Ethernet.
|
|
|
How do other protocols use Ethernet?
|
By putting it's L3 PDU into the data portion of the Ethernet frame.
|
|
|
How does the receiving device know what type of L3 PDU is in the Ethernet frame?
|
Data link protocol headers, including Ethernet, have a field code that defines the protocol header that follows. Called a type field.
|
|
|
What is a type field?
|
A type field would have a value of hexadecimal 0800 (decimal 2048) Other types of L3 PDU would be implied by using a different value in the type field.
|
|
|
Type fields when sending?
|
When sending IP packets if the type field has a value less than hex 0600 (decimal 1536), Another field is needed to identify the type of L3 PDU inside the frame .
|
|
|
To create a type field that use the type/length field as a length field?
|
Either one or two additional headers are added after the Ethernet 802.3 header but before the Layer 3 header. Ex: sending IP packets. Ethernet frame has two additional headers: IEEE 802.2 Logical link control (LLC) header Sub-network Access Protocol header (SNAP)
|
|
|
How does Error Detection work?
|
Errors occur as a result of electrical interface. Data-link protocol covered, Ethernet defines a header and a trailer, the trailer containing a field for error detection.
|
|
|
Ethernet Frame Check Sequence (FCS)
|
It allows a device receiving an Ethernet frame to detect whether the bits have changed during transmission. To detect an error, the sending device calculates a complex mathematical function, the frame contents as input, the result into the frame's 4 byte FCS field.
|
|
|
How does the receiving device calculate the FCS field
|
It does the same math on the frame; if it's calculation matches the FCS field in the frame, then no errors occurred. If it doesn't match the FCS field, than an error has occurred and the frame is discarded.
|
|
|
Ethernet and errors.
|
Errors that are detected on Ethernet frame are discarded, Ethernet does no action to retransmit the frame.
|
|
|
What are the pair layouts for T568a and T568b?
|
|
