Instructor: In this lesson,
we are going to talk about wired connectivity issues.
This includes things like physical connection issues,
cable length issues,
interference issues and port flapping issues.
Now, first, let's talk about physical connections.
Remember, when you're using a wired network connection,
there are lots of different physical components,
and all of these could be the source of your issues.
Now, when you're considering a physical connection
as a source of your connectivity issues,
this might be
because you have some kind of a break in the connection
anywhere along the line.
So as you start considering your different options
of where things can be going wrong,
you need to think about every piece
in that physical connection.
This starts with your client
and it's network interface card.
This NIC or network interface card
is where the network cable
is going to connect into your computer
and transform things from an electrical signal
into a binary one or zero
that can be read and understood by the computer.
Now, moving from our client
and going into our network interface card,
we then come out of that
using that RJ45 connector and it's associated network cable.
This will then connect into a network jack.
Normally in most office environments,
this will be a wall jack
that's going to be using an RJ45 connection.
Once you connect into that wall jack,
on the other side of that,
you have a mini punch down block
on the back of that wall jack,
and this is going to be cabled all the way in through the walls
and over to your patch panel in your network closet.
Once you get to the patch panel,
you're going to connect another patch cable
going from that patch panel
to the particular network device you're connecting to.
Most of the time,
this is going to be a 24 or 48 port switch.
Using that network switch,
your network is going to be able to move traffic
to and from your client and out to the internet
going through a router, a firewall or other gateway.
So if you're having an issue with an unstable connection,
an intermittent connection or no connectivity at all,
it could be that the issue
is with the physical layer of that network
as I just described all these different pieces and parts.
To test this connection from end to end,
you can connect a network cable tester
to the wall jack of your particular port
and then to the patch panel on the other side.
This will test all the interior wiring
going from that wall jack
through the walls and into that patch panel.
If this works properly,
then it's a matter of testing the individual cables,
connecting the wall jack to your client
or the patch panel to your switch.
And if you find a cable that is faulty,
the easiest thing to do is replace that cable.
If you find that the wall jack is faulty
or the connection to the patch panel is faulty,
in those cases,
you'd want to take the cable off of those connectors,
restrip the cable,
and then repunch them down using a proper punch down tool
and then testing that connection from end to end again.
Another quick way
to determine if your network connection is working properly
at the physical layer
is to simply look
at the back of your network interface card.
On the back of your network interface card,
you'll usually have two or three lights on it.
These three lights
are used to indicate the status of the connection,
the activity on that connection
and the speed of that connection.
If you're dealing with the link light,
this will show that you have a valid link
all the way back to the switch.
If you look at the back of your network interface card
and you don't see the link light is actually lit up,
this means you have a physical issue
somewhere along that path
and you need to troubleshoot that
to identify which cable or punch down is incorrect.
Second, you're going to have what's called the activity light.
The activity light will blink
anytime data is being sent or received
through that network interface card.
This is a way to see
if the network is actively sending or receiving information.
That's a great thing to look at
to verify that you have not just a good link,
but you're actually sending data back and forth.
The third light that you'll find
on the back of a network interface card
only exists on some cards,
but this is going to display
what speed that card is operating at.
This could be 10, 100 or 1000 megabits per second
depending on your network interface card.
Normally, this light will be off
if you're using 10 megabits per second,
it'll be orange if you're using 100 megabits per second,
and it'll be green
if you're using the 1000 megabits per second connection
on your network interface card.
The second connectivity issue you might come across
when you're dealing with wired network connectivity
is an issue with your cable length.
If you remember,
we talked about the fact that unshielded twisted pair cables
can only go a maximum of about 100 meters
before you have issues with connectivity.
So you always want to look
at the entire length of the connection
and verify how long it actually is.
Remember, if we're going from the client to the wall jack,
the wall jack to the patch panel
and the patch panel to the switch,
the entire distance along that line
cannot be more than 100 meters.
If it is, you're going to have to use some sort of a repeater
to be able to increase the signal,
or you're going to have connectivity issues.
Now, personally,
I like to keep all of my network connections
under 90 meters instead of 100 meters
because this gives me a little bit of extra padding
in that space requirement
and make sure I don't have any connectivity issues
like I would
if I'm going right up against that 100 meter mark.
Now, the third issue we need to talk about
when it comes to wired network connectivity is interference.
That's right,
interference does affect our wired connections.
When I talk about interference with wired connections,
really this is going to be coming
from an external interference source.
Generally, this will include things like power lines,
fluorescent lighting, motors or generators
that are located near your cables.
For example, I've seen a lot of businesses
that will run their network connections through the ceiling.
And when they do that,
they'll actually have the cables
going directly over one of their fluorescent lights.
Well, anytime those fluorescent lights are on,
it's actually generating extra power
that's being fed into those wires,
and this power
can actually have a source of external interference for us,
and this will actually jumble the ones and zeros
that are being sent across that line.
If you're finding that you have this issue
with external interference,
what you want to do is verify
that your cables are not going across any power lines
or fluorescent lighting in the ceiling.
Additionally, if you have to operate your network cables
near or around power lines,
fluorescent lighting, motors or generators,
you should use a fiber optic connection
instead of an unshielded twisted pair copper connection
because fiber optic cables
transmit their data using light instead of electricity,
and therefore they're immune to that external interference
caused by things like power lines,
fluorescent lighting, motors and generators.
The final wired connectivity issue you need to be aware of
is what's referred to as port flapping.
Now, port flapping is caused
when you have an intermittent connectivity issue
between your client and your network switch.
When you have port flapping,
this can occur either on the client's network interface card
or the switch's interface.
Now, with port flapping,
the status of that network interface
is going to be going up and down continually
from an upstate to a downstate and back.
And this is why it's called port flapping,
because we are flapping from an up or on state
to a down or off state.
Most often, port flapping
is going to be caused by either bad cabling,
external interference
or a faulty network interface card on your client.
In any of these cases,
you need to check your switch configuration interface
and its logs
to be able to see how long
the port is remaining open in an upstate
versus how often it's going into a downstate.
This will help you understand
exactly how bad your problem is,
and then you can go to work
figuring out exactly where this issue is coming from,
whether that's bad cabling somewhere along the line
or some kind of external interference
that's affecting your network cabling.
So remember, when it comes to wired connectivity issues,
you can have four main types.
These are physical connection issues,
cable length issues,
interference issues or port flapping issues.