Hello everyone and welcome to our next section of our Encore Wireless. We're
going to be diving into roaming. Now roaming is very important in our
enterprise environments because we're not always in the same place. You may have
a meeting and it may take you to a conference room or you may be down on
the finance floor and you're usually on sales floor. And you're constantly moving
around in your organization even in campus wide networks let's say. You
need to be able to move around without constantly having to log in and using
different SSIDs and your traffic being rounded different ways. So how do we
manage this from a wireless perspective? I mean wireless is all about
portability. You're obviously not going to drag the wire along with you. So how
do we make it so that that is as seamless as possible to our end users? We
do this through roaming like we said but we have two... let me stop. We have several
types of roaming. There's not just two types but let's talk about two types of
roaming here. I'm going to take myself off the screen so you can see exactly what I'm
talking about. So there is controller roaming where we're actually moving
between our wireless LAN controllers. We talked a little bit about our wireless
LAN controllers in the past. Remember they are that centralized configuration
hub that lightweight APs connect to and look to for management. They're asking
what are my SSIDs? Who's allowed to use them? What should I be advertising? Who
should I allow on which SSID? So this is what the wireless LAN controllers do.
They control the APs. So when I have a user who's on an AP and wants to move to
a different AP, that's when the wireless LAN controller has to come and play. Now
there's two types of controller roaming when I'm moving. There's inter
and intra controller roaming. Inter controller roaming means between wireless LAN
controllers. So I have wireless LAN controller one and I have wireless LAN
controller two. Let's say I'm moving from one wireless LAN controller to another.
Once I do that, that is inter controller roaming. This might be... let's say this is
building... each side of a building, right? Each building. And let's say you're on
decentralized wireless LAN controller architecture. If you don't know that,
that's from our last lesson. And we have another wireless LAN controller for this
second floor. It's a very big building. The west side of the building. But I want to
stay in the same... the exact same SSID. You can see here I'm still in SSID staff.
SSID staff. So I'm moving from one to the other. Now these could be totally
different VLANs. This could be this or that. But what we really want to do is
make sure that they are using the same interface or virtual interface IP
address. Otherwise, the handoff does not complete. Remember this. Please. It's
important. When we are doing a mobility group and we are doing inter wireless
LAN controller roaming, we have to make sure that the virtual IP address is
configured the same in the mobility group. Otherwise, this handoff is gonna
break. We're gonna try and pass the client off here and the client's gonna go
over here and it's gonna go, no. I don't know what you're talking about. My
virtual IP is different from that. The mobility group does not match. I'm done.
One thing to understand. Not a huge deal. This is for smaller environments.
When we have intra wireless LAN controller, that means we're just handing
off from AP to AP. This is very common, even within the same floor of the
building. Sometimes, if the room is big enough, even within the same room, you are
transferred from one AP to another based on your signal strength. Make
sure you know this part. I underlined it. Whenever I underline something, it's very
important. Layer two roaming, and understand this, is when we are
roaming between wireless LAN controllers in the same subnet. If I'm at VLAN
10 here and I'm going to VLAN 10 here in the same SSID, I am doing layer two
roaming, which means I'm not changing my layer three. Layer three, remember, is a
subnet. Layer two means I'm in the same subnet. I'm in the same
wireless LAN. This is sub 20 seconds. I don't know how this, milliseconds,
this is going to happen very, very quickly. The user, most likely, will never
even know it happened. Unless, you know, you're streaming a video while you're
doing this, you might see a little hiccup, and even then, some of the
caching will take care of that. Don't worry about it too much. So, we have this
client association, client one. We see it roam over, and it moves to two. You see
that? I'm going to roll back, just so you can see this fancy graphic. We're going
from here to here. Watch it happen in real time. We're going to move from
wireless LAN controller. There's a handoff. There's a communication between
wireless LAN controllers. Hey, this guy's leaving my cell. It's going to this cell
for AP two. Oh, this is your domain, wireless LAN controller two. You handle
it. It is handed off, and this does take great, this is less than 20 milliseconds.
Now, what about layer three roaming? What are we talking about when layer three
roaming is happening? Well, what we have is an anchor controller and a foreign
controller. I'm going to introduce these two topics to you. Please understand them.
An anchor controller is your original wireless LAN controller. It's where you
start, and then you are moving to another controller. What happens is the original
controller marks the client with an anchor entry, and it gives it this
information in its database. It says, oh, you're on AP one, your association, let's
say the name is client one. You're on the wireless LAN of staff, check. You're on
VLAN 10, check. Okay. I need to move that information over to wireless LAN
controller two because we're doing layer three roaming. Then this moves over, and
this is designated as the foreign controller. This is where we are going.
It's foreign. This is the anchor. This is where I started. This is where all the
data is. I'm going to move this over to the foreign, and then there is a foreign
entry into this new database. Well, let's see what it looks like. Bam, we move over,
but hang on. It's a foreign controller. The VLAN is not the same for these. So
what does it have to do? We create that CAPWAP tunnel we talked about. We're
going to take that traffic and shoot it back over to the anchor. There's a reason
it's called anchor because we have to make sure if we're going to do layer
three roaming that we're on the right subnet. Otherwise, we're toast. No
communication can take place. So this IP address stays the same, but we need to go
back. Let me roll back again. You can see, boom, this is the subnet we're on. We move
over. See, that's 20. We move over. Boom. Did this subnet change? No, it did not.
It's still 20, but look at this. The client is on 10. That's why we have that
CAPWAP tunnel is to get the traffic back. This foreign controller has this
database entry and understands that, hey, this is not the right IP address. I need
to send this back to the anchor to make sure it gets to the right spot. Now,
this is a special circumstance. You're not going to see this a lot. This is not
something that happens a ton. Layer three roaming is a special case, but I want you
to be aware of it. Notice that the roles don't change. This doesn't suddenly
become the anchor after a while. This is always the foreign controller. This is
always the anchor controller, unless the client disconnects and reconnects to the
new SSID, and they would have to have permissions to do so. But this is a very
special case. You might see this in a few places. This is not the norm, but it's
something I would know if I was being tested on this stuff. All right, that's
that's that. Let's talk about software-defined access roaming, SD access
deployments. First off, I want you to be able to identify these immediately. When
you see XTR, that stands for a fabric edge node. XTR, think SDA roaming.
Inter-XDR, across fabric switches. Intra-XDR, within a fabric switch.
So, just so we're clear, this is an edge, single edge fabric switch. Here to here,
intra. And then here to here, you can see, look, these are, this is a fabric switch,
this is a fabric switch. We're going up to the wireless LAN controller. This is
inter, because I'm moving from switch here, AS1, to switch here, let's call AS2.
I've moved from switch to switch. Very important you understand that. But that
is all the roaming we need to cover for this Encore section. This is a very
important section. We only have four slides here, a lot of information on those
slides. All of the information that I talked about is important for your exam
objectives. I'll see you in the next one. Bye.
you