- Let's talk about Automatic Private IP Addressing,
also know as APIPA.
This is something that occurs when,
usually when your computer cannot get an IP address
from a DHCP server.
If you see the address 169.254.X.X,
any other numbers after that,
if you see 169.254,
that means APIPA and chances are that means
that your computer's not getting the correct IP address
from a DHCP server.
And APIPA has kicked in.
This automatic private IP addressing is built
into the Windows system,
and it originally was created
so that Windows could be networked together automatically
without the use of a switch
or a router or anything like that.
But nowadays it kind of just gets in the way
of clients trying to obtain IP addresses,
or it manifests itself
when a client cannot obtain an IP address.
And so what we're gonna do is we're gonna show
an APIPA address in Windows, and then we'll show how
to fix the problem using the IP config command,
and also show in the registry, how to disable APIPA.
So we talked about APIPA
or automatic private IP addressing,
and how it can be a problem sometimes
and could get in the way
of your computer obtaining an IP address automatically.
To be honest with you, I've had texts
where APIPA has just driven them bonkers.
But like any technical problem, it is solvable.
So first of all, what I wanna do is I wanna look
in the command line and see
whether or not APIPA is actually running.
Then we'll go into the registry and show how to turn it off.
So first we'll go to the command prompt now.
And we'll do one of those ipconfig/alls.
And we'll see that we got lots and lots
and lots of information.
Well, we'll start with the wireless lan adapter.
And what we're looking for here
is auto configuration enabled, that is APIPA,
and it says, yes, it's running.
So we know that APIPA is actually functioning.
And so if you ever saw 169.254 here as the IP address,
it's pretty safe to assume that you could say, all right,
this computer was trying to obtain an IP address
from a DHCP server, but it couldn't do so
for one of a variety of reasons.
The DHCP server could be down,
the computer might not be accessing the network properly,
and so on.
And at that point it gets the 169.254,
and the APIPA is applied.
If we look at the other adapter, the ethernet adapter,
we'll see here that yes,
auto configuration is enabled.
Even though we're not doing DHCP,
auto configuration enabled, that's separate.
So APIPA is actually still running on this.
So we know it is actually running and you may
in some environments need to turn it off.
To do that, we'll go to the registry.
And the best way to get there is to go to the run prompt,
and type regedit.
So we'll do our trusty Windows and R combo,
and we'll type regedit here and press enter.
And yes, I had already typed it.
And here's the user account control.
We'll just say yes for that.
And that brings up the registry editor.
So what we wanna do is we wanna locate
where the APIPA configuration is, where we can change that.
And in here, we're gonna go
to HKEY local machine,
system,
current control set,
services,
and we'll scroll all the way down to T C P I P,
because APIPA is part of the TCPIP protocol suite.
And that's here, open that up.
Then we'll go to parameters, and then interfaces.
And finally, we need to know which interface
we wanna turn off.
And you see, these are just associated
with big hexadecimal numbers.
These are security identifiers.
Or they're globally unique identifiers.
Not important for the A plus,
but big hexadecimal numbers associated
with each of our network adapters.
And if we look at these, we can find out which one we want.
This is the guy I want.
The second one.
I know that because of the IP address.
This is my ethernet network adapter, 10.254.254.204.
And it has the default gateway, 10.254.254.1.
All the networking information in here is placed
in here as values.
And you can make modifications from here.
This is really going into depth with the system.
Now, you gotta be careful with the registry.
If you're ever gonna make any changes or add information,
you should back up or export the entire registry,
or at least export the key or sub key
that you're messing with.
And to do that, you just go to file and go to export.
And then you select exactly what you want to back up.
A lot of times,
I'll just back up the entire registry database.
This way you're safe.
If a mistake happens, you could always go back.
So always have that backup or that export.
But what we're gonna do here is we're going
to create a new value, a new DWORD.
So we'll right-click, select new, and then DWORD.
And this is gonna be called IP auto configuration enabled.
And that's all one word.
Make sure we spelled that right.
Ipautoconfigurationenabled, press enter.
That creates the entry.
And now we have to assign a value.
If we press enter for this,
we'll see the actual DWORD configuration.
Right now it's set to zero and that's what we want.
We really can just set it to zero for off,
and one for on.
If we set it to zero, then IP auto configuration enabled,
or APIPA will be turned off.
So that's a little bit about APIPA,
And now you know what it is, why it might happen,
and how you can see whether it's running in Windows,
and also how to turn it off if necessary.
So that's about it for this sublesson.