Section 6 : Ethernet Fundamentals

? connects devices and allows them to talk using protocols

Ethernet

What two ways do devices access the network?

deterministic or contention-based

What is being described ? deterministic or contention-based

very organized and orderly

need an electronic token to transmit

example : token ring networks

deterministic

What is being described ? deterministic or contention-based

collisions can occur

chaotic

devices transmit whenever they want

example : ethernet networks

lower overhead

contention-based

What protocol prevents collisions? this allows ethernet devices to access the network contention based effectively

CSMA/CD

what does CSMA/CD stand for

carrier sense multiple access / collision detection

break down CSMA/CD into three parts, Carrier sense, multiple access, and collision detection what does each part do ?

Carrier sense : looks for gaps in the convo and listens to the wire, verifying that it is not busy

Multiple access : meaning all devices have access at any time. they can all access, listen to, and transmit to the network

Collision detection : if two devices transmit at the same time, they will both back off at the same time, waiting a random time ( like 3 and 8 secs and try again )

what is being described? a device’s reaction to a collision, they will both back off at the same time, waiting a random time ( like 3 and 8 secs and try again )

random back off timer

What do we call an area that shares a part of the Ethernet segment ( everything on the same cable or hub )

collision domain

devices operate at —- duplex when connected to a hub ( layer 1 device ) because if it was full duplex devices would hear themselves

half duplex

these devices increase scalability of the network by creating multiple collision domains, more collision domains are a good thing

switch

why can switches operate in full duplex mode and hubs cant?

each port on a switch is its own collision domain. so there is no chance of collisions because that device is communicating directly to the switch on its own collision domain. on a hub all devices are heard so they must wait and listen before transmitting.

what are the two primary devices used in our networks?

routers and switches

what did routers and switches evolve from?

bridge, and hubs

Which device is being described?

• known as multiport repeaters

• three types : passive, active, smart

• layer 1 device used to connect multiple network devices/workstations

Hubs

what type of hub is being described?

repeats signal with no amplifications

does not require external power supply

passive hub

what type of hub is being described?

repeats signal with amplification

requires an external power supply

active hub

what type of hub is being described?

active hub with enhanced features like snmp

smart hub

Switches operate at what layer (typically) and use what address to make forwarding decisions

layer 2, mac addresses

Each port on a switch represents an individual ?

collision domain

all ports on a switch belong to the same ?

broadcast domain

Routers operate at what layer and make forwarding decisions based off of which address?

Layer 3, ip address

On a router, each port is a seperate ? and what ?

collision domain and broadcast domain

What are 7 features found in a switch

VLANs

trunking

STP spanning tree protocol

link aggregation

port monitoring

power over Ethernet ( PoE )

user authentication

Which switch feature is being described? and what is the protocol #

combines multiple ports on a switch to form a single virtual connection to increase bandwidth availability, efficiency, and application resiliency

link aggregation 802.3.ad

Which switch feature is being described?

Supplies electrical power over ethernet to devices without the need of a power cable requiring CAT 5 cable or higher

Power over Ethernet PoE

What are the two different forms of poe?

PoE 802.3af & 802.3at

what is the difference between 802.3 af and 802.3 at?

the wattage power that is delivered. af delivers 15.4 watts of power while at delivers 25.5 W of power

which poe is referring to as PoE+

802.3at

what are the two device types to describe how poe powers them?

PSE power sourcing equipment

PD Powered devices

which device type is being described?

is going to provide the power to our other devices, normally your switch

PSE - power sourcing equipment

which device type is being described?

devices getting power over ethernet from power source equipment, i.e VOIP phone, wireless access point (wap)

PD Powered device

What is used to analyze packet flow over the network?

port monitoring or mirroring

what is the difference when it comes to analyzing packets using port monitoring between hubs and switches

because hubs broadcast everything to every port you only need to add a network sniffer to your hub to analyze traffic, but switches must have port monitoring configured on the device in order to allow the traffic to be mirrored out to a network analyst machine ( such as wireshark) over one particular port. example: on a 24 port switch you can mirror traffic from ports 1-23 and have your remaining port open to mirror traffic over it to the network analyst machine

Which switch feature is being described? and its protocol #

• for security purposes, switches require users to authenticate themselves before gaining access to the network by granting a key that is shared between the supplicant , device wanting access, and the authenticator ( switch ).

  • this key is used to encrypt traffic from and being sent to the client

User authentication 802.1x

what are two options to configure and manage switches?

SSH secure shell ( remote access )

console port ( more secure than ssh )

what allows for local administration of the switch using a separate laptop and a rollerover cable ( DB-9 to RJ-45) i.e allows for direct communication and control of the device have to be there locally

console port

what involves keeping all network configuration devices on a separate network, i.e creating another network that sits on top of your network that you use for your data. only used to connect and configure devices.

out-of-band (OOB)

What protocol creates virtual IP and MAC addresses to provide a “active router” and a “standby router” . this is a cisco proprietary protocol

Hot standby Router Protocol HSRP

First hop redundancy involves which network device?

layer 3 switch

what are the four First hop redundancy protocols discussed in this section?

HSRP Hot standby router protocol

GLBP gateway load balancing protocol

VRRP virtual router redundancy protocol

CARP common address redundancy protocol

which protocol permits redundant links between switches and prevents traffic loops ? protocol # as well

availability is measured in 9’s

five 9’s is 99.999% uptime and allows only 5 minutes down per year

without it mac address table corruption can occur

Spanning Tree Protocol STP ( 802.1D)

What standard forwards traffic based on priority markings?

QoS quality of service

What can occur if you don’t have STP, spanning tree protocol ?

broadcast storms

if a switch doesn’t have STP you have to —- the switch to kill the broadcast storm

unplug

what is elected to act as a reference point for a spanning tree? the switch with the lowest bridge ID (BID) will be elected as this

Root bridge

all other switches in an STP topology that are not the root bridge are referred to as?

nonroot bridge