Network troubleshooting methodology.

In this lesson, we're going to discuss

the official CompTIA Network troubleshooting methodology.

This is the first thing that we need to cover

in this overall section,

on troubleshooting physical networks.

Now we're going to cover domain five network troubleshooting,

specifically objectives, 5.1 and 5.2 in this section.

Objective 5.1 states that you must explain

the network troubleshooting methodology,

which we're going to fully cover in this lesson.

Then in this section, we're going to move through

and talk about objective 5.2,

which states that given a scenario,

you must troubleshoot common cable connectivity issues

and select the appropriate tools.

We're going to spend the rest of this section

focused on that objective, but for now,

let's focus our attention

on the network troubleshooting methodology.

After all, much of your day as a network technician

is going to be spent entering trouble tickets

or fixing problems that are found inside of your networks.

To help us with this, we have a seven-step

troubleshooting methodology that we can use

to solve any problem inside of our network.

There are seven steps here,

the first is to identify the problem.

Second, establish a theory of probable cause.

Third, test the theory to determine the cause.

Fourth, establish a plan of action to resolve the problem

and identify potential effects.

Fifth, implement the solution or escalate as necessary,

sixth, verify full system functionality and if applicable,

implement preventative measures,

and seventh, document findings, actions, outcomes,

and lessons learned.

All right, let's take a look at each of these seven steps

in a little bit more depth.

Step one, identify the problem.

This is our first step in the troubleshooting process,

and it's used to clearly understand what the issue is

that you're trying to solve.

This problem may have been reported to you by an end user,

an administrator or through some automated alert.

It really doesn't matter,

whatever the original report method used,

your goal now is to get more information

so you can fully understand that issue

that you're trying to solve and get things back to normal.

As we attempt to identify the problem,

we have to gather additional information,

question our users, to gather more details,

identify symptoms of the issue and determine

if anything has changed.

Then we're going to try to duplicate or reproduce

the problem if possible, sometimes though,

you may have multiple problems occurring at the same time.

And if this is the case, you should approach

each of those problems individually

and not bundle them together as a single problem

or shared problem, unless you figure out

that they are clearly linked,

because sometimes they're not clearly linked.

All right, let's take a look at what this might look like

in the real world.

Let's pretend you're sitting at the service desk

and an end user calls up and states,

"The internet is down, the internet is down.

"I can't do anything right now, I need your help."

Well, what are you going to do?

As a network technician, you probably know

the internet is not down completely,

but it's really just a problem with a user's connection

to the internet that may be slow, unresponsive,

or simply not connected.

But maybe the user was trying to open Facebook

and they got an error message and told them

there is no internet connection,

so to them, the internet is down, but we all know

the internet is made up of millions of different

computer networks, and the chances of the entire internet

being down is pretty darn slim.

So what are you going to do about this?

Well, first you should ask some additional questions

to the user, let's ask them things like,

what were you doing at the time of the error,

or what websites are you trying to access?

As you ask them questions, you might also ask

what type of connection they have.

Are they using a wired connection, wifi, cellular

or something else entirely.

As you ask more questions, you're gaining more information

and this can help you identify the symptoms

and determine if anything has changed.

For example, you might ask, when was the last time

you connected to that website?

And if their answer was an hour ago, then you should ask,

did you install, remove any programs since then,

or has anything changed in the last hour?

As you gather more information, it's going to help you

figure out what's going on.

All of this falls under that first step

of identifying the problem.

Step two is to establish a theory of probable cause.

This is the second step in our troubleshooting process,

and it's used to come up with a possible solution

to the problem you clearly identified back in step one.

When we establish a theory of probable cause,

we need to question the obvious first, for example,

if the end user said they normally connect to the internet,

using a wifi connection on their laptop, you may want to check

that they haven't turned off the wifi card,

using the toggle switch on that laptop by accident.

If they did, then of course the internet is going to be down

because they've turned off all wireless capability

on that laptop at the physical layer of the OSI model.

Also, when you're establishing your theory of probable cause

you should use multiple approaches to solving the issue.

This could be a top-to-bottom approach,

a bottom-to-top approach or a divide and conquer approach.

A top-to-bottom approach relies on troubleshooting

from layer seven of the OSI model down to layer one.

So we start the application layer and we work our way down.

A bottom-to-top approach, instead relies

on troubleshooting from layer one of the OSI model

up to layer seven of the OSI model.

Here we start at the physical layer by checking our cables

and wireless radio-frequency connections

and then we work our way up to layer two, switching,

layer three, routing, and continue all the way up

through four, five, six, until we get to seven

at the application layer.

Now the divide and conquer approach is used when we split

the network or the layers of the OSI model in half

and troubleshoot from there.

Early in my career, I used to work

as a nuclear reactor operator,

and when I was troubleshooting electrical circuits,

we often used this divide and conquer approach.

We called it half-splitting,

but it's essentially the same concept.

Essentially, we would figure out what the halfway point was

in the electrical circuit, and then we tested

the connection there.

If it worked, it meant the first half of the circuit

was good and I didn't have to look at the first half anymore

because everything was working properly.

Then I could focus on the second half.

Now I could half-split again between the halfway point

and the end and I could troubleshoot again

until I found where the problem was.

We kept doing this over and over until we found the error

and it really was a quick way to figure things out.

Now, we can do the exact same thing in our networks.

If I'm trying to troubleshoot the internet is down issue

for this end user, I could figure out

what the halfway point is between their computer

and the internet, which would probably be

our default gateway.

I could then try to send a ping from the end-user's computer

to the default gateway.

If it works, that means my internal network

is functioning fully, and the problem exists

between my default gateway and the internet connection

or the distant web server.

Now, this is my halfway point and with a single ping,

I already verified the entire internal network is working

from the end user, all the way up to the gateway.

This is my divide and conquer approach at work,

also known as half-splitting if you use my terminology.

Now at this point in step two, we're just coming up

with a theory of what might be going wrong,

such as I think the default router is down

and preventing the end user from accessing the internet,

but we're not trying to solve it yet,

that will come in step three.

So step three is test the theory to determine the cause.

So now we've looked at the problem in step two

and we've created our theory, we need to actually test

that theory here in step three.

This is where we actually begin to take some actions

such as pinging the default gateway

from the end user's workstation or checking

network configuration on a particular router,

switch or firewall.

If the theory is confirmed, then we're going to determine

what our next steps are going to be

to solve the bigger issue.

If the theory remains unconfirmed,

then we're going to have to reestablish a new theory

or escalate the issue to a higher tier

or more senior technician,

who may have additional privileges or more knowledge

on how to fix this issue.

Step four, we're going to establish a plan of action

to resolve the problem and identify the potential effects.

At this point, we now want to build out a plan of action

to resolve this issue.

Let's go back to our internet is down issue.

We found that the default router was causing the issue,

we pinged it, and in step three, we found that traffic

was not getting out of the network

and going past this default router.

Now we can log into that modem from the ISP and verify

it had a good connection to the internet,

so we know the issue is definitely something

to do with the router.

Some reason that router is not passing traffic

to the internet, but the modem and the connection is up.

So we're going to look at that router, and we find out

that the CPU utilization is between 90% and 100%.

We now have a theory that if we reboot the router,

we could clear this high CPU utilization and the traffic

would again, start to flow through this router.

Now, as you establish your plan of action here in step four,

to reboot this router, we also need to identify

the potential effects.

This is an enterprise level router,

so it'll take at least 10 to 15 minutes to reboot it.

During that time, traffic will be unable to be routed

through this router from the internal network

to the internet.

Now, that's not really a big deal here

because the internet was down, right?

And so all of our users can't access the internet anyway,

because the router's not passing traffic to it.

But this router may also be used to pass traffic

to, and from your DMZ, your data center

and other client villains.

So during that reboot, the entire network,

internal and external, will be essentially down.

Now you need to weigh this potential effect

with the action you want to take.

And in most cases, you're going to have to get approval

from your supervisors or the IT director

to reboot this router, to solve the internet issue,

even though in the next 10 to 15 minutes,

you're going to cause a network wide outage

by rebooting this router.

All right, next step five, implement the solution

or escalate as necessary.

At this point, we've briefed our plan

and we've gotten permission,

now we're going to implement the solution.

In our example, that would be rebooting the gateway router.

Now, if you don't have administrative rights to do this,

or the solution is beyond the scope of your abilities,

you may escalate this to the next higher level technicians

to deal with this problem.

For example, you may be a level one network technician,

and you simply don't have the proper permissions

to reboot this enterprise grade router,

or maybe the router was completely dead

and need to be replaced, so you need a level two

or level three engineer to put a new router in the rack,

cable it up, load up the baseline configurations

and get it working again.

This would require an escalation of this problem

to get it solved by these level two

or level three technicians.

All right, next step six, verify full system functionality

and if applicable, implement preventative measures.

Now, the solution has been implemented here either by you

or the higher level technicians, now, we need to verify

it actually solved the initial problem.

So maybe we rebooted the router and then we try to connect

to the website again from the end-user's computer.

Did it work?

If so, great, we've solved the issue.

If not, we need to return to establishing a new theory

and then we're going to go through the whole troubleshooting

process again, to figure out how to solve it.

Again, if there was some kind of cause or outage

to this problem, we also want to implement

preventative measures to prevent it from happening again.

For example, maybe this router was having

this excessively high CPU utilization

because there was a routing loop.

If this is the case, we need to go in

and change the configurations to prevent a routing loop

from occurring again in the future.

Also, we may need to go back and train

our network administrators who have caused that routing loop

so we can show them how to avoid them in the future.

This is all considered methods to prevent a recurrence

of this particular issue.

Finally, step seven, document findings, actions,

outcomes, and lessons learned.

Now that the crisis is behind us and the problem is solved,

we want to document what went wrong and what we did about it

and what those results were, and anything else

that we learned so we can share this with others,

so this problem doesn't happen again.

All right, I know this was a lot of steps,

but if you're using the standard network

troubleshooting methodology, it will really help you

to ensure you're thinking through all the possible issues,

developing a theory, creating a plan of action

and implementing it to successfully solve

challenging issues when you're in the field.

For the exam, you need to memorize these seven steps

in the order that they're listed,

it would be very fair for CompTIA to ask you on test day,

what these seven steps are, and they can place them

in a random order and ask you to drag and drop them

into the right order for those seven steps.

Or you can get a question that says,

you're troubleshooting a network issue,

and you just establish a theory of probable cause,

what is your next step?

And you'd have to say,

test the theory to determine the cause.

Now remember, these seven steps of network troubleshooting

are the methodology that we're going to use

and you have to memorize them.

One, identify the problem, two, establish a theory

of probable cause, three, test the theory

to determine the cause, four, establish a plan of action

to resolve the problem and identify potential effects.

Five, implement the solution or escalate as necessary,

six, verify full system functionality,

and if applicable implement preventative measures

and seven, document findings, actions,

outcomes, and lessons learned.

Cable Review.

In this lesson, we're going to do a quick review

of the different specifications,

limitations, considerations,

and applications of network cables.

First, let's consider the different specifications

and limitations of our twisted pair copper cables

in terms of throughput, speed, and distance.

CAT 5, also known as Fast Ethernet or 100BASE-TX,

operates at 100 megabits per second

at a distance of up to 100 meters.

CAT 5e, known as Gigabit Ethernet or 1000BASE-T,

operates at 1,000 megabits per second

or 1 gigabit per second at a distance of up to 100 meters.

CAT 6, also known as 1000BASE-T or 10GBASE-T

can operate at 1,000 megabits per second,

or 1 gigabit per second

at a distance up to a 100 meters,

or it can reach speeds of 10 gigabits per second

at a distance of up to 55 meters.

CAT 6a and CAT 7 are also known as 10GBASE-T,

and both of these operate at 10 gigabits per second

at a distance of up to a 100 meters.

CAT 8 is also known as 40GBASE-T,

and it operates at 40 gigabits per second

at distance of up to 30 meters.

All right, let's consider the different specifications

and limitations of our coaxial

and twinaxial copper cables

in terms of throughput, speed, and distance.

Coaxial cables can support speeds

of up to a 100 megabits per second

at a distance of up to 500 meters when using ethernet.

Now, coaxial cables can offer us this longer distance

over a twisted pair cable,

but they can't reach the higher speeds

that twisted pair cables can reach

in our modern networks.

Twinaxial cables though can support higher speeds

of up to 10 gigabits per second,

but they're limited to a distance of only 5 meters or less.

Newer twinaxial cables can also increase their speeds

up to 100 gigabits per second

at a maximum distance of 7 meters.

But again, these are not mainstreaming use yet.

Next, let's consider the different specifications

and limitations of our fiber cables

in terms of throughput, speed, and distance.

100BASE-FX operates at 100 megabits per second

at a distance of up to 2 kilometers

using a multimode fiber.

100BASE-SX is going to operate at 100 megabits per second

at distance of up to 300 meters using a multi-mode fiber.

1000BASE-SX is going to operate at 1,000 megabits per second,

or 1 gigabit per second for a distance of up to 220 meters

to 500 meters or more using a multi-mode fiber.

1000BASE-LX is going to operate at 1,000 megabits per second

or 1 gigabit per second

at a distance of up to 550 meters using a multi-mode fiber

and up to 5 kilometers

if we're using a single-mode fiber.

Now 10GBASE-SR is going to operate at 10 gigabits per second

at a distance of up to 400 meters using a multimode fiber.

10GBASE-LR is going to operate at 10 gigabits per second

at a distance of up to 10 kilometers

using a single-mode fiber.

Next, we need to discuss some cable considerations,

such as shielded versus unshielded,

and plenum versus riser rated.

First, we have two types of twisted pair cable,

shielded and unshielded.

At their core,

both shielded and unshielded twisted pair of cables

are created the exact same way.

The only difference is that shielded twisted pair cables

have each of their individual pairs of wires

wrapped in a foil shielding.

This gives them a little bit more protection from EMI.

Then all four of those wrapped pairs

are also wrapped with another foil layer

for some additional protection.

This extra shielding does help protect

the shielded twisted pair cables

from electromagnetic interference

and power frequency interruptions,

but it does add cost to it,

making shielded twisted pair more expensive

than unshielded twisted pair,

so you really only use it

for specific business cases and applications.

For example, let's say you're running a network inside

of a radio station or an airport,

those areas are placed

with a lot of electromagnetic interference,

so you probably want to opt to use shielded twisted pair

to provide the network

with a little bit of extra protection.

Additionally, if you're running a twisted pair network

inside of a factory

with heavy machinery or generators,

it's also going to be a good idea

to use shielded twisted pair here

because there's extra frequencies of EMI

that are going to be exposed to your cables.

Now, if you're truly worried

about electromagnetic interference or EMI though

it would actually be a better idea

to upgrade to a fiber-based network

because fiber cables are truly immune to EMI

because they rely on light signals instead

of electrical impulses to send their data.

Now, unshielded twisted pair of cabling on the other hand

is also used in a lot of our local area networks

because it's inexpensive, easy to install, lightweight,

and really flexible.

Regardless of whether you're going to use shielded twisted pair

or unshielded twisted pair,

you need to keep your cable lengths

under the maximum recommended length of 100 meters.

Next, we have to think about plenum

versus riser rated cables.

Now, plenum cables are going to be used

when the cable is going to be run

in the spaces between the ceiling and the floor above it,

such as where you put your heating

and air conditioning duct work.

Now, these plenum cables have a higher fire rating

and they're designed with fire retardant plastic jackets

that use low smoke PVC

or fluorinated ethanol polymer known as FEP.

Now, usually plenum rated cables are going to be used

when you're running cables horizontally in your building

across a particular level.

Riser cables on the other hand,

are going to be used to run network cables vertically

between the floors in a building

inside a cable riser or an elevator shaft.

These riser cables are used in non plenum areas as well.

These cables are built with special coatings

that allow them to self extinguish,

and they prevent the flame from burning through the cable

and traveling upwards between the floors.

Now, building codes are specific

to the location of the building itself,

and they're going to be determined

by your state or county that you live in.

In general, most fire and building codes

will allow plenum cables to be used

in both plenum and riser spaces,

but riser cables can only be used in the risers

and not in plenum spaces.

This is because riser cables are not made from PVC or FEP,

and therefore they can actually release chemicals

and smoke into the air ducts if they caught fire.

Finally, let's take a look

at some cable applications you may come across

when working as a network technician.

These include things like rollover and console cables,

crossover cables,

and power over ethernet.

Now, a rollover or console cable

is a type of null modem cable

that's used to connect a computer terminal

to a router's console port.

This cable is typically flat

and has a light blue color to it

to help you distinguish it from other networking cables.

Typically, one side of the cable has an RJ 45 connector

that's used to connect directly to a router's console port.

The other side of the cable traditionally

has a DB 9 serial connection

that'll connect to a laptop computer.

This specialized cable is used to allow the technician

to directly connect to the router

and make changes to the configuration

as a form of out-of-band communication.

Now, a crossover cable is a special type of network cable

that's used to connect two ethernet devices directly.

So if you have two computers

and you don't have a switcher router between them,

you can use a crossover cable to connect them.

They're also used to send and receive data

by enabling complex data transfers

between two computers two routers,

or two other network devices.

Usually a crossover cable is created

by using a TIA 568 B pinout on one side of the cable

and the TIA 568 A pinout on the other side of the cable.

If you need to connect a computer to a computer,

a router to a router, a switch to a switch

then you're going to use a crossover cable.

Now finally, we have power over ethernet.

Power over ethernet or PoE

is a technology that passes electrical power

over twisted pair ethernet cables to powered devices.

Now, this can be done to go to a wireless access point,

an IP camera,

or VoIP phone to give them data

and power on the same cable.

This enables one cable to give you both data

and electrical power to these power devices instead

of having to have a separate cable for each

making it really easy to install things

like IP security cameras.

To support power over ethernet,

you need to have at least a category 5E

or better copper twisted pair cable.

Otherwise, it's not going to function right

and it could be dangerous.

Now, power over ethernet can provide 15.4 to 60 watts

of power using two of the twisted pairs inside of the cable

or you can get 60 to a hundred watts of power

if you're using all four

of the twisted pairs inside of a cable.

Just like other twisted pair cable installations,

power over ethernet can only transmit data and power

up to the maximum distance of 100 meters.

Alright, I know that was a lot of information

and I gave it to you really quick,

but I hope you found this quick review of copper

and fiber cables and all their different specifications

limitations, considerations,

and applications helpful

as you're preparing for your exam.

Cabling tools.

In this lesson, we're going to discuss the various tools we use

when working at the physical layer of our networks,

especially with copper and fiber cabling.

This includes snips and cutters, cable strippers,

cable crimpers, cable testers,

wire maps, cable certifiers, multimeters,

punch down tools, tone generators,

loopback adapters, time-domain reflectometers,

optical time-domain reflectometers,

fiber light meters, fusion splicers,

taps and a spectrum analyzer.

Woo, lots of stuff we're going to cover.

All right, the first cabling tool we have

is probably the most basic one that we're going to cover

and it's a snip or a cutter.

A snipper or a cutter is used

to simply cut a piece of cable off of a larger spool

or run of cable.

Now, a snip looks a lot like a pair of scissors,

but it has stronger blades because we're going to use it

to cut off twisted pair of copper cables,

coaxial cables or even larger cable bundles.

Next, we have cable strippers.

Now, once we cut the piece of cabling off the larger spool

using our snips, we now need to strip off the end

of the cable and prepare it for attachment

to a plastic RJ45 connector

or whatever kind of connector we're going to use.

For example, let's say I wanted to create a crossover cable.

I'm going to cut off some twisted copper from the spool,

then I'm going to strip both ends using a cable stripper.

This allows me to remove around six to 12 inches

from the outer plastic jacket at the end of the cable

and then I can spread out those inner wires,

prepare to attach the RJ45 connector to them

and then I'm going to have to use a crimper to do that.

Now, if I'm making a coaxial cable,

I would then use a coaxial specific wire stripper

to remove the outer jacket of the cable

and the insulation, so I can now get to that center conduit

for that RG6 connector to go through

and be put on the end of that cable.

Next, we're going to use a cable crimper

and this is how we attach the connector

to the end of the cable.

Again, let's say I'm making that crossover cable.

I need to use an RJ45 connector

and RJ45 specific cable crimper.

Normally your cable crimper is going to be used

for twisted pair cabling

and it's going to support both RJ45 and RJ11 connectors.

If you're working with coaxial cables,

there's a different cable crimper you'll use

that'll support RJ6 or RG59 connectors.

All right, now that we've created our cable

using our snips and cutters, our cable stripper

and our cable crimper, we need to test the cable

and this is where we use a cable tester.

A cable tester is going to be used to verify the continuity

of each of the eight individual wires

inside of that twisted pair of cable.

This will verify there's no breaks inside the cable

and that we have good continuity from one end to the other.

By using a cable tester,

we can verify the pin outs were done properly

and that each individual wire in the twisted pair of cable

is properly connected for a straight-through

or crossover cable, whichever one we were making.

Now, there are different types of testers

for different types of cable.

If you're testing an ethernet cable,

you're going to need one with an RJ45 connector

on the cable and that cable tester.

Now, if you work with a lot of different types

of networks though, you may want to use a multi tester.

A multi-tasker isn't going to support

just ethernet cables using RJ45,

but it can also support BNC connectors for coaxial cables,

IDE connectors for hard drives, pata and sata connectors

for internal computer devices, RJ45,

again for your ethernet, RJ11 for your telephones,

fiber, DB25, DB9s and anything else you might need to test.

Next, we have a wire mapping tool.

Now a wire map tool is like a cable tester,

but it works specifically for twisted pair ethernet cables.

In addition to testing the cable from end-to-end,

we can diagnose any issues with that cable,

such as an open pair, a shorted pair,

a short between the pairs, a reverse pair,

a cross pair or a split pair.

Now, an open pair occurs when one or more conductors

in the pair are not connected on one of the pins

at either end of the cable.

In other words, the electrical continuity

of the conductor is being interrupted.

This can occur if the conductor

has been physically broken somewhere in the middle

or because you had an incomplete or improper punch down

on a patch panel.

Now, a short can occur when conductors of a wire pair

are connected to each other

at any location within the cable.

A short between the pairs occurs

when the conductors of two wires in different pairs

are connected at any location within the cable.

A reverse pair occurs when two wires in a single pair

are connected to the opposite pins of that pair

on the other end of the cable

and cross pairs occur when both wires of one color pair

are connected to the pins of a different color pair

on the opposite end.

Split pairs occur when a wire from one pair

is split away from the other

and crosses over the wire into an adjacent pair.

Because this type of fault

essentially requires the same mistake to be made

at both ends of the cable,

it usually doesn't happen very often

unless somebody meant to do it.

Next, we have a cable certifier.

Now, a cable certifier is used

with an existing cable to determine its category

or data throughput.

I can plug into your network and find out,

is it a CAT5, CAT6, CAT5e, CAT7 or CAT8 network.

It's going to tell me

based on the frequency range being used,

what the throughput of the cables are

and the standard output is shown here on the screen,

as you can see.

Now, notice I have a wire mapping here

that shows my pins are correct,

that it's a straight-through cable.

It's also going to tell me how long this cable is.

In this case, it knows it's 10 feet.

Then it's going to tell me what the delay is on the cable.

It tells me what the resistance is on the cable.

All that type of good information can be gotten

from a cable certifier.

Essentially, it can do a lot of the same functions

as a cable tester, but it goes further

and gives you additional details

such as length and throughput.

So I can use this to determine the length

and make sure it's right for a particular cable

or if the cable has been crimped properly,

just like a cable tester does,

but all this other information is really good too.

Now, because of all this extra information,

these devices are more expensive.

When you're dealing with a simple cable tester,

you can buy that for about $10,

but a cable certifier might cost you 100 or 200 or $300.

Next, we have a multimeter.

A multimeter is a way to check the voltage

or amperage or the resistance of a copper cable.

This can used to verify if a cable is broken or not

by checking its resistance.

Now, if I check a copper cable from end-to-end,

I should get something at zero resistance or zero ohms,

because the center of that wire is pure copper.

Now, if there's a high level of resistance or an overload,

that means there's a break in the cable somewhere.

Now, multimeters can be used to check coaxial cables as well

to ensure there's no cuts or breaks

in the middle of a patch run

or it can be used to test power sources and power cords.

For example, before I plug a computer

or a switch or a router into an outlet,

I might want to check that outlet

and verify I'm getting the right voltage.

Is it getting 115 to 125 volts here in America?

That would be right.

If I'm in Europe, I should be getting 230 to 240 volts.

Either way, I can test that using my multimeter

and make sure I'm getting good, clean, reliable power

before I connect my very expensive switches,

routers and other gear into those power outlets.

Next, we have a punch down block.

If I'm going to be using a 66 block or a 110 block

for either my phones or my networks

or even my network jacks in the wall,

I'm going to be using punch down tools to install those cables.

This is going to terminate the wire on the punch down block

and strip off the excess installation

and trimming off all the extra wires that we no longer need.

Next, we have a tone generator, also known as a toner probe.

Now, a tone generator allows a technician

to generate a tone on one end of the connection

and use the probe to audibly detect

the wire connected on the other side.

This is often called a fox and hound,

because the fox generates the tone

and then the hound is used to sniff it out

and find it using that toner probe.

A tone generator is going to be used to understand

where the cables are running inside of your walls

whenever you have an unlabeled or undocumented network

and you need to figure out which wire

is connected to which jack inside your building.

Next, we have a loopback adapter or loopback device.

These loopback adapters are going to be different

depending on whether or not you're using ethernet

or fiber in your networks.

Now, if you're using twisted pair cabling in your networks,

you can create your own inexpensive loopback adapter

by simply connecting some of the twisted pair of wires

from the transmit side to the receive pins

inside the same RJ45 connector.

Essentially, you need to have your transmit plus

going to your receive plus,

which means pin one goes to pin three,

then you need transmit minus going to receive minus.

This is pin two going to pin six.

If you're using fiber in your networks,

you can simply connect your transmit port

to your receive port using a fiber patch cable

and this creates a loopback for you.

This is extremely easy to do

if you're using an ST or SC connection

and they do make specialized loopback plugs

in a small form factor,

so you can carry these in your pocket

when you're working as a network technician.

Now, once you connect your loopback adapter to your network,

you can then use specialized diagnostic software

to test the connectivity of the client

and ensure everything's working properly.

Next, we have a TDR,

which is known as a time-domain reflectometer.

Now, a time-domain reflectometer

is going to locate breaks in a copper cable

and provide an estimate of the severity

and the distance to that break.

If I have cable running underground between two buildings

and I need to figure out where it's broken,

because my network stopped working

and I need to dig a hole and fix that,

I can use a TDR to look at exactly where that break is.

When the TDR is run, it's going to report back

that there's a break at approximately 87 feet away

and now I know exactly where to dig,

being able to access that cable and then patch that cable.

Now there's also an optical version of this,

called an optical time-domain reflectometer or OTDR.

This is going to be used for fiber optic cables.

It works the same way,

but instead of using the resistance of the wire,

we're using light and the bounce back for it.

This is really helpful, especially with fiber optic cables,

because remember, your fiber optic cables

can be many, many miles long

and so knowing that the break is at 3.57 miles away

is a lot more useful than trying to figure out

where it is on your own.

This is going to be essential

if you're using fiber underground,

then you want to make sure you have an OTDR,

because you won't be able to visually inspect

your fiber if it's buried.

Next, we have a fiber light meter,

also known as an optical power meter.

Now, a fiber light meter is a device

that provides a continuous wave of stable source of energy

for attenuation measurements.

Essentially, this device is going to include a source,

like a laser or an LED and it's going to be stabilized

using an automatic gain control mechanism,

so we can accurately measure how effective

a fiber optic cable is transmitting that light.

If you're using multimode fibers,

you're going to use an LED-based fiber light meter.

If you're using single mode fibers,

you need to use a laser-based fiber light meter.

Basically, you're going to connect one part

of the fiber light meter

to each end of the fiber connection.

One end is going to send light down the fiber,

the other end is going to measure how much is being received.

Then it's going to report back to you in decibels,

the amount of loss experienced

as the light traveled along the cable.

If the loss is higher than 0.5 decibels,

both ends of the fiber should be cleaned,

polished and retested once more.

Next, we have fusion splicers.

Now, a fusion splicer is a machine

that's used to permanently join two fibers together.

If you have a break in a fiber cable,

a fusion splicer is going to be used to cut out that break

and then reconnect or splice them back together again.

If you're dealing with a fiber patch cable,

I wouldn't bother using a fusion splicer.

Instead, you're just going to replace the cable,

but if you have a really long fiber cable

running between two buildings or across the city,

that is a time where it's going to be a lot cheaper

to fix that broken fiber by using a fusion splicer

than it would be to dig up

and replace the entire cable again.

Fusion splicers are going to require training

to properly use them and it's a very specialized skillset

and a job for a network technician

who works a lot with fiber networks.

I'll tell you personally, I've never used a fusion splicer.

I've hired people when I had that need.

Next, we have a tap.

A tap is a simple device that connects directly

to the cable infrastructure

and splits or copies those packets for use in analysis,

security or general network management.

You're going to need to purchase

and install the appropriate tap for your type of network,

depending on if you're using copper or fiber.

Now, basically you're going to connect the tap inline

to your network and it's going to create a duplicate copy

of every frame, one going out the tap port,

where it's going to be collected

and analyzed by your cybersecurity tool set

and the other one out to your network,

so it can be processed by the equipment.

This is used heavily in cybersecurity,

but it can also be used in network management

and network operations.

Finally, we have a spectrum analyzer,

a spectrum analyzer is a device that measures

and displays the signal amplitude

or the strength as it varies by frequency

within its frequency range known as the spectrum.

Now, the frequency is going to appear on the X-axis

or the horizontal access

and the amplitude is going to be displayed on the Y-axis

or the vertical axis.

A spectrum analyzer is going to be used

to measure the electrical signals

that are being passed over that medium.

Now, the medium could be a copper cable,

such as ethernet or coaxial

or it could be a radio frequency

if you're listening to a particular radio wave.

If you're working with a satellite connection, for instance,

you might use a spectrum analyzer to ensure your modem

and radio are properly sending

and receiving the carrier waves to and from that satellite.

Again, this is a more specialized tool

that most entry-level network technicians

are not going to find themselves operating.

All right, I know that was a lot of different tools

that we just covered.

Remember, when you're dealing with the physical layer

of your network, especially if you're dealing

with copper or fiber cabling,

you're going to be using a lot of different tools

for a lot of different things.

This includes things like snips and cutters,

cable strippers, cable crimpers, cable testers,

wire maps, cable certifiers, multimeters,

punch down tools, tone generators, loopback adapters,

time-domain reflectometers,

optical timed-domain reflectometers, fiber light meters,

fusion splicers, taps and spectrum analyzers.

For the exam, it's important for you to understand

which tool you might use to troubleshoot

which type of cable and which type of issue.

Cable signal issues.

In this video, we're going to discuss the various issues

you may experience with connectivity

that are caused by cable signaling issues.

This includes attenuation, interference, and decibel loss.

First, we have attenuation.

Attenuation is the loss of signal strength

on a network cable or connection

over the length of the cable.

This is a common occurrence in both wired

and wireless connections.

But for right now, we're going to focus

on wired connections only.

When we're using a copper cable,

such as a twisted pair or a coaxial cable,

we're going to transmit data across the cable

by sending electrical signals of varying voltages

that represent our binary ones and zeros

of the data being sent.

The copper conduit inside these cables

are going to carry those signals,

but that copper has a natural level of resistance,

and the longer the cable becomes

the higher that resistance becomes

and the data has a harder time

traveling down the copper cable.

This causes the signal to weaken or attenuate

as it travels along the distance of the cable.

When you learned about twisted pair cables

in our ethernet connections, I told you

that we had this maximum distance of about 100 meters.

Now, this is caused because of attenuation.

Once you get further than 100 meters,

the signal is going to weaken and become unreliable.

With coaxial cables, you have more shielding

or insulation around it, therefore you can reach distances

of up to about 500 meters.

But when you pass that limit, the attenuation again

becomes too much and the signal strength weekends

to an unusable level.

So, distance is going to be our main factor

when we're dealing with attenuation.

But there's a couple other factors

that can affect your signal strength too.

This includes frequencies that are used by the connection,

the noise in the environment

and the physical surroundings near the connection.

You see, all networking and electrical cables operate

at a specific frequency.

For example, power cables in a residential or office setting

are usually going to operate at 60 Hertz

in the United States and Canada.

But, if you're in another country,

it may operate at 50 Hertz.

Ethernet cables though operate at different frequencies too.

If you're using a CAT 5e cable, for instance,

it uses a frequency of 100 megahertz,

while a CAT 6 cable is going to use a frequency

of 250 megahertz.

A CAT 6a cable uses a frequency of 500 megahertz,

and a CAT 7 cable uses a frequency of 600 megahertz.

Now, in general, the higher the frequency

the higher the bandwidth that your particular cable

is going to be able to produce.

This is because each hertz

is one cycle per second in frequency.

And so, the more cycles you have in a second,

the more times you can put a one or a zero down that cable.

So, if you're going to use a network cable

that uses a frequency similar to the frequencies

of the cables surrounding it,

you can have something known as crosstalk

or interference that's going to occur.

Now, this brings us to the concept

of noise in your environment.

If there's additional electrical frequency

or radio-frequency noise in your area,

this can cause your network cables to have problems

and increase the rate of attenuation

and decrease in your associated signal strength.

For example, if you have a network cable

that's located near an area where heavy machinery

or power generators are being used,

this will create noise and signal interference

that will decrease the distance

that cable is going to be able to support

because there's more attenuation and more noise

across that signal.

Finally, the physical surroundings

you're using your copper cables in

can also increase your attenuation.

Things like temperature, the construction of the walls

or other barriers, and the type of wire installation itself

can all negatively affect your signal strength.

If you have freezing temperatures for instance,

your copper cables will become more brittle and inflexible,

which in turn slows down the connection

and attenuates the signal.

When you're experiencing hotter temperatures,

the signals can actually overheat and the network cable

could potentially even catch fire

if the outside plastic melts away and the inside wire

becomes exposed to flammable materials.

For this reason, it's always important

to have well-insulated wires and attempt to maintain

the proper temperature control

that your network connection needs

to maintain a strong signal and minimal attenuation.

So, what can you do when you experience attenuation?

First, you can make sure you're using the proper cables

for the physical environment you're operating within.

If you're operating in a hotter or colder environment,

you may need to switch to shielded twisted pair

instead of unshielded twisted pair for example.

Second, you can shorten the distance.

While the maximum length is 100 meters for these cables,

it's a good idea to use cables

that are a bit shorter than that

to ensure you always have a good, clear signal

on all of your connections.

Personally, I tend to implement an 80 meter limit

on all of my twisted pair cables inside my networks.

Third, you can use an amplifier or a repeater.

These are layer one devices

that take in the signal on one end, boost up the signal,

and retransmit it out the other side.

This means if I need to run a twisted pair cable

over 150 meters, I could use a 75 or a 80 meter cable

connected to a repeater, and then I can go the next 75

to 80 meters to make the total 150 meters.

By using this repeater, there's going to be no signal loss

because we essentially rebroadcast out a new signal again

from that repeater as we start over our distance limitation.

If you're dealing with fiber cables

instead of copper cables, you have a lot of the same issues

in terms of attenuation because of distance,

but, they don't begin to occur until much further out.

This is because we're using light

instead of electricity here.

Now, for example, let's say you have a single mode fiber

that has a maximum distance of 40 kilometers.

You're not going to really suffer much signal loss

until you get around 30 to 40 kilometers from your source

depending on your environmental conditions.

Another cause of attenuation in fiber cables

tends to occur if you have cheaply constructed fiber cables

or you have fiber cables that have dirty connectors.

Let's imagine you have a pair of sunglasses on,

and you have fingerprints all over the lenses,

that makes it really hard to see through them, right?

Because you have dirty glasses.

Well, the same thing happens with fiber connectors.

When you're dealing with fiber connections

and your fiber connectors are dirty,

this can lead to signal loss and attenuation

because the light can't cleanly pass

through those connectors because it's dirty.

This adds to attenuation and signal loss for you.

Now, if you're experiencing this attenuation

with fiber cables, the first thing I recommend you do

is change out the fiber cable for a higher quality cable

or you clean and polish both ends of that fiber

and make sure those connectors are really clean.

You want to make sure there is not a dirty connector there

because even something as little as your fingerprints on it

can cause this attenuation to occur.

Next, we have interference.

Interference occurs when multiple cables operate

in the same frequency band

and they operate in close proximity to each other.

To help prevent this,

we want to use high quality twisted pair cables

or use higher category rated cables.

Now, this is because higher category rated cables

are going to have more internal twist per inch

inside their internal twisted pairs.

These internal twists can help overcome the interference

that can occur within a single cable

inside of its own wired twisted pairs.

Now additionally, if you see a twisted pair

of network cable that's being run over

or near a high power cable,

this can cause interference as well

and a large amount of signal loss.

To solve this problem, you always want to plan your cable runs

to operate in parallel and not directly next

to any high power cables running in your cable trays

or your risers.

Finally, we have decibel or dB loss.

Now, decibel loss is used to measure

the amount of signal deterioration that we're experiencing

on a given connection.

This can be used to measure the signal

on a copper or fiber cable.

For copper cables, we see this reported as a dB loss,

to represent the amount of voltage that has decreased

since we sent the signal out originally

over that twisted pair cable.

For fiber connections though,

this dB loss is instead going to represent

the amount of light that's lost as it travels

across the cable or the connection.

If you're experiencing a high amount of dB loss

on a copper cable, you need to replace that cable

with a higher quality twisted pair cable

with additional shielding

or a higher number of twists per inch.

If you're experiencing a high amount of dB loss

on a fiber cable, you want to replace that cable

with a higher quality fiber cable,

such as a glass one instead of a plastic one.

Or you need to clean and polish both ends of your cable

and the associated connectors.

All right, we just covered our three big

cable signaling issues that you're going to experience

in the field as a network technician.

Just a reminder, these are attenuation,

interference, and decibel loss.

When you're testing your network for attenuation conditions,

always use a cable certifier

to measure the amount of attenuation.

For fiber connections, you're going to use a fiber light meter

to test for attenuation as well.

If you need to test a connection for interference,

you can connect a spectrum analyzer to the cable

to see the exact frequencies and signals

that are being sent over that connection.

If you want to test for decibel loss,

you're going to use a cable certifier, a cable analyzer,

or a fiber light meter to measure the signal being sent

and received across a given cable

and report back that loss in decibels.

For the exam, it's important to understand

the tool you might use to troubleshoot

the different cable connectivity issues.

Copper cable issues.

Now, in this lesson,

we're going to discuss the various copper cable issues

that you may experience.

This includes things like incorrect pinouts,

bad ports, opens, and shorts.

First, we have incorrect pinouts.

If you're testing a twisted pair of network connection,

and it isn't working properly,

the chances are, your connections pinout

is probably incorrect.

Now, there are a few places

that connections pinout could be incorrect,

including the patch panel, the wall jack,

or the RJ45 connector itself.

When you look at the patch panel,

there's usually going to be a sticker

near the punch-down block that shows you what wire or pin

should be attached to each connection point

on that patch panel.

By default, most patch panels use a TIA 568B pinout.

This means we have pins one through eight

being connected as white/orange, orange,

white/green, blue, white/blue, green,

white/brown and brown.

If you're having an issue with the connection

and you suspect the pinout is incorrect,

you need to visually inspect

the back of the patch panel and it's punch-down block

to ensure the proper colors

are being put in the proper pins.

Now, when you're looking at the back of a wall jack,

the exact same thing holds true.

Instead of being shown as pins one through eight

in a horizontal layout like you might see in a patch panel,

most wall jacks will usually have

four pins on one end of the jack,

and four pins on the other.

This wall jack is also known as a keystone.

And it's clearly going to be labeled as pins one through eight,

or visually using color code stickers or markers

for each pin's location.

Finally, we have our RJ45 connector itself.

These plastic connectors are using net copper pins

to the inner twisted pair wires of a UTP or STP cable.

While an RJ45 is not clearly labeled from pin one to eight,

or with the TIA 568B color scheme you need,

you can always visually look at the pins

and see all eight pins inside the RJ45 connector.

When you hold up the RJ45 connector

with a small plastic clip facing downward,

you can then look at the pins

and count them from left to right,

numbered from one to eight.

Again, this will ensure

that your inner twisted pair wires

are color coded correctly

as white/orange, orange, white/green, blue,

white/blue, green, white/brown, brown,

when you view it from pin one to pin eight.

To test the connection or a cable and verify its pinout,

you can also use a cable tester or a wire mapping tool.

These tools will test the inner wire

from your cable or connection,

and ensure they're properly cabled

from one end to the other.

If the connection is found to be incorrectly pinned out,

you can simply disconnect the individual wires,

re-strip the twisted pair cable using a wire stripper,

and re-punch down the wires

into the patch panel or wall jack,

or replace the RJ45 connector on the cable

until all portions are properly using

the TIA 568B wiring standards.

Next, we have the issue of bad ports in a copper network.

Each network interface card on a workstation or server

needs to connect to an ethernet twisted pair network,

is going to have an ethernet port,

that it's going to use and accept an RJ45 connector into.

If you need to test the ethernet port

on your network interface card,

you're going to need to use a loopback plug,

and specialized software.

This will let you send out data

and have it returned back in the ethernet port,

and determine if everything's functioning properly.

If it isn't,

you need to replace the network interface card.

If the network interface card

is soldered to your motherboard,

you can then add an expansion card instead

to replace this broken onboard ethernet port.

Now, if you suspect a bad port on a switch or a router,

you need to connect a loopback plug

to the port on that device

and run a test using specialized software,

just like you would on a workstation.

Now, if the port is found to be faulty or bad,

you can then switch out any connections from that port

to another available port on the switch or router.

In the case of a router,

you may also be able to replace the ethernet port

by changing out the interface card

for the router on that slot.

If not, you're going to have to simply move that connection

to another available port.

Finally, we have opens and shorts.

When you conduct a cable test of a twisted pair connection,

you may find an open or a short exists

on that cable connection.

The result of open is going to occur during a cable test,

if you have nothing on the other end of the connection,

or if there's some kind of a break in the wires

between the source and the destination.

So, if I'm conducting a test of a cable

from a patch panel to the wall jack,

over a patch cable into my tester,

and it reports as open,

that means somewhere in that end-to-end connection,

it's either disconnected,

or one of those cables

has been accidentally cut or broken.

At that point, we're going to need

to test each piece of the connection

to determine where that break exists.

For example, I might first test the patch cable.

And if that's successful,

I know that the problem isn't my patch cable,

and instead, I'm going to look at the patch panel connection,

or the wall jack connection.

The opposite of an open is considered a short.

Now a short indicates that two wires are connected together,

somewhere in that connection.

Usually, this occurs when a cable is poorly made,

or two of the inner twisted pair wires

are accidentally touching each other

in a single pin of an RJ45 connector.

If you're experiencing a short in your connection,

you should rewire the RJ45 connection

at the end of the cable,

as this is usually going to be the source of your problem.

If this doesn't fix it,

then you need to physically examine the entire cable

to see if it's been damaged

somewhere in the middle of that cable run.

Alternatively, you can simply replace the cable

with a known good cable,

and this can also solve your issue.

If you need to test for incorrect pinouts,

opens, and shorts, a good cable tester, a cable certifier,

or a wire mapping tool will be the key to your success.

If you're testing for a bad port,

then a loopback adaptor or a loopback plug

is going to be the tool to use.

Remember, for the exam,

it's important to understand

which tool you might need to use

to troubleshoot different cable connectivity issues.

Fiber cable issues.

In this lesson, we're going to discuss

the various fiber cable issues you may experience

such as incorrect transceivers,

transmit and receive being reversed,

or dirty optical cables.

Now, first, we might experience issues

with incorrect transceivers.

A transceiver is a transmitter and receiver

in a single device.

Transceivers are going to be used

to convert a network connection from one type to another,

and they work at layer one of the OSI model.

In your routers and switches,

it's common to use a transceiver for your fiber connections,

but if you're going to be using the wrong transceiver,

this connection simply won't work.

Many transceivers are considered hot pluggable,

and they can be taken out, replaced

without shutting down the associate router,

switch or SAN device.

If a transceiver fails and you need to replace it,

this becomes quite easy

since you can simply unplug the bad transceiver

and plug in your replacement.

But you need to ensure

you're using the correct transceiver,

otherwise, you're going to have problems.

If you put in the wrong type of SFP transceiver,

you're going to have data loss

and a loss of connectivity over time.

Remember, transceivers are designed

to support a certain type of connection

and a certain type of cable.

If you're using a long wave SFP transceiver,

but then connect a short wave fiber cable to them,

that's not going to work.

Therefore, if you have a device that's no longer working

and you recently changed out your transceiver,

you should go back and double-check

that you're using the right model for your device

and your associate cabling.

Next, we can sometimes have issues

when our transmit and receive ends are being reversed.

Now, while this may occur

in a twisted pair network occasionally,

this is really going to be the biggest issue

inside your fiber-based networks.

Remember, most of our fiber connections

are going to consist of two individual cables,

one for transmission of data

and one for receiving that data.

For example, if you're connecting a switch

to a workstation using a network interface card

that has ST connections on it,

one of those is going to be labeled TX for transmit.

The other one is going to be RX for receive.

Now, if you connect the transmit cable

to the RX connection,

and the receive cable to the TX connection,

you're not going to get a valid link

or connection to that switch.

If this happens, you can quickly identify and fix this

by simply disconnecting the TX and RX port cables

and swapping those cables.

Then, when you do that,

you can check the LED link activity lights on your NIC,

and you're going to see the link is now online and available

as indicated by a solid orange light

or a blinking orange light

if the network is actively communicating again.

Finally, we have dirty optical cables.

Dirty fiber optic cables and connectors

can cause major performance issues

or connection problems inside your network.

A dirty fiber just means something is interfering

with the clear optical connection between the cable,

the connector, and the connection port

for the fiber connection.

Even something as small as some dust,

or dirt, or your fingerprints

can really severely block the light

being sent down that cable.

Now, remember, multi-mode fibers

are only 50 to 62 microns in diameter,

so it really doesn't take much

to block these connections.

If you find yourself with a dirty optical cable

or connector,

you really just need to clean it

using a dry cleaning or wet cleaning method.

Dry cleaning involves simply using light pressure

while rubbing the end face of a fiber cable

or connector using a dry cleaning cloth

in one direction.

This will usually be used when you need to clean dust

or dirt off the face of a connector.

This same technique can be used for a fiber connection port

on a switch or network interface card too.

Wet cleaning involves lightly moistening

a piece of lint-free cloth

with a fiber optic cleaning solution,

and then wiping the end face of the cable

in one direction as well.

This cleaning solution

should be 91% or higher isopropanol alcohol

if you're using a solution.

Now, wet cleaning is considered more invasive

than dry cleaning,

but it is useful when trying to remove oil residues

or films off those cables and connectors,

such as if somebody has put their fingerprints on them.

You're going to have to use wet cleaning

to get those fingerprints off.

Now, if you start receiving a large amount of errors

over a fiber connection,

or your performance begins to slow down,

it could be the indication

that you need to clean a dirty fiber.

This can also be quantitatively determined

if you're using a fiber light meter,

because you can compare the decibel reading

from your baseline of a clean fiber

versus this dirty fiber.

Ethernet issues.

In this video we're going to discuss

the various Ethernet issues that you may experience

such as duplexing issues,

and how you can troubleshoot different issues

using LED status indicators.

So let's talk first about those LED status indicators.

These tend to be used to diagnose an issue

in both fiber optic and copper connections.

Most of your network interface cards

are going to have two lights on the back of that card.

One for an activity light and one for a link speed light.

Now the activity light is going to be used to show

the status of the link when it's in used.

If the activity light is off

that means there's no link,

or connection being established.

If the activity light is solid orange

this indicates there's a link or a connection established

with this network interface card,

and the upstream device that it's connected to

such as your switch.

But when you start to see that light blinking orange,

this indicates there's data activity

occurring over that link or connection.

So if you're trying to determine if the issue exists

with the network interface card, or the network itself,

a quick look at that activity light can be a good hint

during your network troubleshooting.

Because if you see an orange light,

either solid or blinking,

this means there's a valid connection or link

between your NIC and the switch.

The second light you're going to find on a NIC

is the link speed light.

Now the speed LED will either be off, orange, or green,

depending on the speed

of the network interface cards connection.

If your connection is operating at one gigabit per second

you're going to see a green light.

If you have 100 megabit per second connection

you're going to see an orange light,

if it's off that's going to indicate you're operating

at a slow speed of 10 megabits per second.

These settings may change depending

on your network interface card,

but for most NICs this is a pretty accurate description.

Now, these lights aren't just used with the NICs though

in a workstation or server,

you also are going to have your network switches

having similar LEDs for each Ethernet port that they have

so you can determine very quickly by looking at it

the status and activity level for each port on that switch.

Next, we have duplexing issues.

Now the most common duplexing issue is a duplex mismatch.

A duplex mismatch can occur

when two ends of an Ethernet connection

attempt to negotiate a full duplex connection,

but one of those devices

thinks the connection is full duplex,

and the other one thinks it's half duplex.

Now, you can identify this type of condition

by observing a high rate of packet loss

without the high rate of jitter

that would normally be typical of congestion.

Also, you're going to see a high received error rate,

and runt packets showing up

when you're using a duplex mismatch.

Now to prevent a duplex mismatch,

you should ensure both devices are configured

to use auto negotiate

when they're establishing their connections.

If they fail to auto negotiate the connection themselves,

you can manually configure them as full duplex,

or half duplex depending on your network conditions.

Remember, your conditions should be set to full duplex

if you're using switches on your network,

because each switch port is considered

its own collision domain.