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Alright, here's our challenge scenario.

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We have a network here and we've got some wireless LAN controllers, a couple of

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layer

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two switches, and then this layer three device here in the middle, creating

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layer three segmentation

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among some of the wireless LAN controllers that otherwise would just have layer

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two connections

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because these layer two switches are just going to carry VLAN straight across.

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So the scenario is that we are this person down here at the bottom.

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We've got a mobile device and we're going to take a stroll.
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We've got a mobile device and we're going to take a stroll.

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We're going to walk from one end of the network to the other, physically, and

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we're going

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to start on access point one here, and then we're going to roam to access point

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two and

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from there, roam to access point three and so on and so forth.

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And so what I want to have us do from a challenge perspective is, first of all,

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we're going

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to identify the roaming type.

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We talked about those three different roaming types in the lightweight

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architecture.

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So let's go ahead and start with that.
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So let's go ahead and start with that.

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Second of all, we want to identify whether there's an anchor controller

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involved with

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this specific roam.

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And finally, what I'd like to do is identify where the point of presence is for

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our device.

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So if our device sends a wireless packet into the network, where does the

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network first

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see it show up?

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Now, just to be clear, once again, we have layer three device in the middle.

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These are layer two switches, and all of these here are representing our capweb
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These are layer two switches, and all of these here are representing our capweb

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tunnels.

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So go ahead and pause the video, take a moment to answer these three questions

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on a per-roam

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basis.

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For example, as I roamed from access point one to access point two, what is the

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roaming

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type?

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Do we need an anchor controller?

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And what is the point of presence?

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Namely, which switch do I first show up on?

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All right, so hopefully that was enough time for you to hit the pause button

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and answer

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these questions.

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It's a great exercise for helping us to identify what exactly is happening here
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It's a great exercise for helping us to identify what exactly is happening here

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with our wireless

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network.

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So let's go ahead and start with moving from access point one to access point

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two.

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As we see, this is staying within the same wireless LAN controller.

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So this is going to be known as that intra layer two roam.

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intra controller means that it's within the same controller, and if it's within

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the same

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controller, it's always going to be layer two.

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So we don't need an anchor controller, because generally speaking, we're only

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going to need

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one if it's a layer three roam, and our point of presence is going to be right
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one if it's a layer three roam, and our point of presence is going to be right

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here.

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We're going to be showing up on this interface on this switch when we get to

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access point

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two.

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So next we roam to access point three here.

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We are now on access point three, which is on this wireless LAN controller.

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So we went for we're going from this WLC to this WLC down here, and now check

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it out.

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We are going across this layer three boundary.

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We're going from this wireless LAN controller down to here.
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We're going from this wireless LAN controller down to here.

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So in this scenario, we are going to have this be an inter, meaning we're

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between two

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different wireless LAN controllers.

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And then again, we're going across a layer three boundary.

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So this is inter layer three.

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So that's the roaming type.

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We do need an anchor.

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Absolutely, we're going to need an anchor controller for this roam, because it

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's layer

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three.

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And lastly, our point of presence is actually believe it or not the exact same.

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So this is what might trick us up a little bit with this scenario.
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So this is what might trick us up a little bit with this scenario.

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Remember, the use of the anchor controllers to say this is my anchor.

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And as I roam across, let's do it like this.

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But I roam to access point three here, now, yes, I'm attached to access point

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three, but

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as traffic comes in from a layer three perspective, it's going to get routed

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towards where that

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subnet lives, which is where the anchor controller lives.

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And so even though there's communication back and forth here, my packet is
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And so even though there's communication back and forth here, my packet is

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going to go to

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the anchor controller and then show up on that switch up there.

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So clean up our diagram, just a little bit here, but do understand that the

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point of

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presence is once again, in the same location.

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Now next, we're going to roam from a one wireless lane controller here to this

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wireless

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lane controller.

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Now I will say this, given the use of anchor controllers and all of these

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things, we're

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kind of treating each one of these as a separate scenario.
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kind of treating each one of these as a separate scenario.

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So if we're migrating, if we're roaming from one foreign controller to another,

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the anchor

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controller is actually going to stay that whole time.

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And so this creates an interesting situation.

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So let's just go ahead and evaluate this one step at a time.

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So we are going to make this an inter controller roam.

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However, there's only a layer two boundary in the path here.

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There's no layer three boundary.

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So this is inter layer two.

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This means that I can stay on the same subnet.

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But again, this was a foreign controller, which just means that this is going
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But again, this was a foreign controller, which just means that this is going

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to be my

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new foreign controller.

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And I'm going to keep the anchor controller in place.

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So if that was your answer to say that, hey, my point of presence stays where

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the anchor

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is, then that's actually a perfectly viable solution in this situation.

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If however, we took this as saying, hey, I'm going to start over, let's say

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that now

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I'm just using this as my initial wireless lane controller.

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And now I'm migrating over to this wireless lane controller, while an inter
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And now I'm migrating over to this wireless lane controller, while an inter

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layer two

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isn't going to use an anchor.

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And it is going to make it so that my point of presence now belongs with the

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new wireless

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lane controller.

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So either one of these would work depending on whether you felt like you're

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starting over

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or whether we were going to continue to use that anchor controller.

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And lastly, we're going to see something similar here as we migrate to access

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point five.

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We're going back across that layer three boundary, which means that it is inter

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, meaning multiple

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wireless lane controllers, and it's layer three, meaning we will need an anchor
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wireless lane controllers, and it's layer three, meaning we will need an anchor

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controller.

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And our point of presence is going to be wherever the, whoops, it's a really

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wrong spot, wherever

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the anchor controller is.

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So if this is our anchor controller in this situation, then it would be there.

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If we're continuing to pass around the foreign controller, then it gets

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interesting because

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we're going back to the scenario up here.

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But as we see, it's a pretty fascinating conversation to unpack this

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architecture because we do

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have to track which type of room we're talking about and also, hey, as I roam
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have to track which type of room we're talking about and also, hey, as I roam

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from access

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point to access point, my station might be bouncing around from one wireless

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lane controller

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to another.

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And a lot of our networks for the most part will largely see most of our APs be

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part of

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a set of wireless lane controllers that are in the same location.

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And that would largely be intra and inter layer two rooms.

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But in the real world, we might have a situation again, campus.

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I walked to an adjacent building.

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It might have different subnets.
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It might have different subnets.

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It might be part of a different wireless lane controller, whatever the

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situation.

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Now we're going to potentially use that anchor concept.

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And always remember as well that the anchor concept can be used intentionally,

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especially

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for guest traffic forming a guest anchor controller that goes into the DMZ.

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I hope this has been informative for you and I'd like to thank you for viewing.  www.technet24.ir