Alright everyone, welcome to the fourth installment of our Encore wireless exam focus dive into
all that is wireless in the Encore world.
So now we're going to talk about the AP discovery and join process.
Now there's been a lot that we've talked about.
We've talked about frequencies, we've talked about antenna types, we talked about AP placement,
and we're kind of going quickly through that.
That's because this is focused on what you need to know for the exam.
I do suggest that you guys, when you have time, take a wireless course to better understand
some of the principles behind this and maybe some of the background information that we're
kind of steamrolling over just to get you the information you need.
So let's talk about the AP discovery and join process really quickly.
Now when we're talking about this process, what you have to remember is when we are looking
at the Cisco product, it's really meant to be an AP, let me roll back here, an AP and
a wireless LAN controller.
And really this is what's called a lightweight access AP or LWAP or one of the billions of
acronyms we use in this industry, but a lightweight access point and a wireless LAN controller.
Now what happens with a lightweight access point is it doesn't have everything it needs
to run a wireless network.
It relies on a manager or a controller and that is the wireless LAN controller.
And we create what's called a CAPWAP tunnel that goes from a lightweight access point
to a wireless LAN controller.
And all the traffic in there is contained in this tunnel.
Now this tunnel may traverse a switch, it may traverse a router, but you really don't
see that.
The traffic doesn't really have a way to escape.
It is directly taken to the wireless LAN controller.
You can study more on that later, but that's kind of outside the scope of our Encore course.
Let's talk about this process specifically.
So an AP sends a CAPWAP discovery request to a wireless LAN controller, basically asking,
is there any wireless LAN controllers I can talk to?
And what happens is any wireless LAN controller it can reach will respond, yeah, I'm here,
go ahead.
And in some environments that may be one, it may be two, it may be three, it may be
four.
It just depends on your environment and how far the lightweight access point can reach.
So all the wireless LAN controllers respond that receive the discovery request.
It's important you understand that.
It sends the response that, hey, I'm here.
Now the wireless LAN controller does not choose whether or not the AP joins.
It's not the one that's going to decide which wireless LAN controller takes on this access
point.
It's the access point itself that chooses the wireless LAN controller it wants to join.
Now a wireless LAN controller can deny that request based on traffic, or maybe it's already
overloaded, or maybe there's something happening that it's not doing well and it just doesn't
want the traffic.
So the AP chooses who they want, then the wireless LAN controller sends the join response,
okay, fine, I will manage your AP.
This is important to understand that we are using CAPWAP, LWAP is old or legacy, but we
are using the CAPWAP protocol and that's why we call them CAPWAP tunnels.
These are the control and provision of wireless access points.
That's what we're doing with that protocol.
Now the discovery phase is more than just a broadcast, that's the first try.
I'm going to try and broadcast a message on a local network and see if any wireless LAN
controller responds.
It can also check previously joined wireless LAN controllers.
Let's say I have an AP and for some reason I remove the AP and add it later.
By adding it later, back to the network, what I'm saying is, oh, I'm back.
And what the AP is going to do is it's going to look at its list of older wireless LAN
controllers it's joined previously and it's going to attempt to join them.
And it can keep up to a list of eight and that just depends on the model you're using.
Next up, we can also use DHCP option 43.
Now many of you know DHCP as the way we hand out IP addresses, the default gateway, subnet
masks, that kind of networking information.
Option 43 is additional vendor information, additional vendor.
That means I can put additional information in there, extra information.
In this case, I can put my wireless LAN controller location, its vendor, who it is, what it's
trying to do, like you can actually add in information so that when that AP boots up
on the network and pulls DHCP, boom, it already has the information for the wireless LAN controller
or controllers on the network.
I can also set up a DNS record.
Now, this DNS record has to be mapped so that here, this ciscocapwapcontroller.localdomain
is mapped to the wireless LAN controller IP address.
Know this, please.
Know this DNS record.
Know that.
Yeah, I said it.
You should probably know that.
And then lastly, we have the AP configuration manually.
Usually, you can use an Ethernet.
If your AP has it, you can use an Ethernet cord or a rollover cord, depending on the model, or even a USB,
depending, again, on the model, to log in directly to the AP and manually configure through GUI or CLI,
again, depending on the model.
You can actually enter this information in so it can contact the wireless LAN controller directly.
Now, we are going to dive very deep into this.
And we're going to dive very deep into it, not because you're going to have to do this in the real world,
but because it's something you might need to understand if you were going to take the exam.
Okay, I'm going to take myself off the screen.
Warning, this is a little complicated.
This is something that I personally would never do without a calculator,
but this is something that I want you to be able to do if you were using a dry erase marker and a dry erase board.
Okay, so let's talk about actually configuring option 43.
Here, this is a Windows Server implementation of DHCP.
And you can see here, we have our available options.
We're going with option 43, vendor-specific info.
That's checked.
And you can see here where it says under binary, we have this hexadecimal value.
Believe it or not, this hexadecimal value tells me things.
I can see right now that we're dealing with a Cisco wireless LAN controller.
I can see that I'm dealing with a specific one IP address, so one wireless LAN controller.
And here, believe it or not, I can see the actual IP address there.
Yeah, so let's dive into how I know these things and how you can get to know these things as well.
So figuring out this value, the TLV value.
Okay, F1 is always.
This means Cisco wireless LAN controller.
So F1 is what we're always going to see right here at the beginning.
That part's easy.
Now, the number of wireless LAN controllers, how did I know that?
Well, this type value, this is pretty easy.
The number of controllers times four.
So if I have one controller times four, the value here is going to be 04.
We're talking about hexadecimal.
If my value of two IPV would be eight, we would be looking at a value of what?
If I have two wireless LAN controllers, we multiply that by four, we get a value of eight.
This would then be eight.
Okay, so the number of wireless LAN controllers multiplied by four.
Next up is the hard one.
We have to do a translation from an IP address into binary and then from binary into hexadecimal.
I'm very sorry.
If I was doing this in the real world, I would 100% use a calculator.
And I would 100% tell any junior administrator who asked me to use a calculator.
But for this exam, I want you to know how to do this, okay?
So you go ahead and convert 172 into binary.
If you do not remember how to do this, it's time to do some brushing up.
If you do the math, we're going to take 172 and dot a decimal.
That's the first octet right here of the IP address of the wireless LAN controller.
And then we're going to turn that into binary, 10101100.
Hmm, okay.
That makes sense.
Remember your place values.
What is that value?
That's 01, that's 20.
What's that?
40, remember we're doing our values here.
So, now we need to break it out into nibbles or four bits.
So we take the 1010 and we break that from the 1100.
All right, we've broken that apart.
Now we can convert this back into a hexadecimal number.
All right, so if we take the 1010, what's the value here?
Well, if this is 1 and that's 2 and that's 4 and that's 8,
if we add the 2 bit and the 8 bit, we get how much?
What's our value?
Our value is 10.
Well, 0 through 9, hexadecimal, what comes after 9?
10, 10 is represented as A. There we go, A.
Let's take our values again.
This is 1, this is 2, this is 4, this is 8.
Remember, our binary dotted decimal places, their value,
the 1 bit is set to 0, so that's 0.
The 2 bit is set to 0, so it's 8 plus 4 here.
Those are the values I have.
What's 8 plus 4?
12.
Well, we know A is 10, B is 11, C is 12.
All right, so we know it's C. So 1010
is A1100C.
All I do is I keep going through those numbers
and I plug it in here.
Notice the A gets plugged in right there.
The C gets plugged in right there.
And as I continue through this calculation,
I keep adding numbers.
Now, luckily, if I was going to test you on this,
I wouldn't test you past here.
So you don't have to do this a ton.
But be aware of how to do it.
It's really important.
Know your place values in binary.
Know how to do a conversion from binary into hex,
from dotted decimal into binary.
And know that F1 is always what we start with.
And then we multiply the number of controllers by 4
to get this value here.
I know.
It's a pretty tough one.
But I believe you guys will do OK.
If you need to, study that more than once.
Go through that portion more than once.
Next, let's talk about discovery outside
of a local area network.
I'm going to have to take myself off the slides again.
I'm right in the middle of it.
So let's say if I have a local area network,
but my wireless LAN controller is outside of that,
I'm going to need to configure an IP helper address.
Many of you have done this already or have done this.
If you haven't, this is the configuration below.
You can see I have a distribution switch.
This is a layer 3 switch.
I have config, interface, VLAN, then the number,
let's say 100 in this case, and then IP helper address
and where I'm going.
That's all.
This is very similar to a DHCP relay agent
that you might set up.
But this time, we're just using it as a helper address.
What we're telling this lightweight access protocol to do
is, hey, I know you're in this VLAN right here,
but if you need to get to this wireless LAN controller,
we're going to actually help you
and push you out into the right space.
That's what this configuration does.
All right, just make sure you understand
how that configuration works.
Interface, VLAN, the VLAN number, IP helper address,
and then the IP address where we're going.
Again, this is the join phase.
We use the encrypted between AP manager and AP.
It's wireless LAN controller.
AP decisions process priority.
This is the priority for that join phase.
Wireless LAN controller, it's used in the past.
So the history, it's going to rely on that first.
It's going to look at the primary controller,
and then it's going to choose the wireless LAN controller
with the lowest number of APs.
This is the AP's decision process.
Remember, if I rolled all the way back,
if I kept rolling the slides back,
remember that process where I said,
the AP decides what wireless LAN controller to join?
This is that.
This is what it uses to make that decision.
It goes with its history, what it's joined before,
what it knows works.
Then it goes to who's the primary controller,
and then if it doesn't know that,
then it goes with the wireless LAN controller
with the lowest number of APs.
That does not necessarily mean
that the wireless LAN controller
is absolutely going to accept the AP,
but that's who the AP is going to choose
and is going to send that join request to.
So what happens after we're completely done with all that?
Let me throw myself back on screen here real quick.
Well, when we're done with all that,
there needs to be a few things to wrap things up.
We have to make sure that the image,
the iOS, the operating system of the AP
matches the wireless LAN controller in compatibility.
And if not, you're going to have to look for updates.
We're going to have to do a configuration check
to make sure that that AP has an OS
that can work with that wireless LAN controller.
Otherwise, you got to start over, right?
It makes sense.
It needs to be compatible.
Configuration check, do you need to do updates?
And in this day and age,
you absolutely, if you're bringing an older wireless AP,
any AP on your network, make sure it's up to date,
especially with all the security patches
and everything else that's going on,
make sure you're fully up to date.
And then last but not least, register your device.
I don't know how many environments have I been in in my life
where people just don't register things.
Register your device.
It gives you warranty access.
It allows you to call up tax support.
It's an important step in the process.
So that was our discovery and join process.
I know there was some difficult stuff in there.
Please review that until you get an understanding
of how that works.
It's a difficult process,
but very important to not only your Cisco certification path
but just understanding in general how it works
and maybe it's a cool party trick.
I'm not sure.
Anyways, thanks for watching.
I'll see you in the next video.
Bye for now.