Introduction to Wireless LAN

Lessons Discussion
1

This topic is to discuss the following lesson::

3

Simple yet effective explanation.thanks.

  1. Can you plz tell me where does these Access Points connect in an enterprise network. what extra feature is required on Accesslayer switches so that can support these LWAPs?
  2. Do These APs connect via a physical cable to AccessLayer switches ?

thanks
Abhishek

4

Hello Abhishek

Let me answer your second question first: Yes, the APs connect via a physical cable to the Access Layer switches.

Concerning your first question, don’t confuse the terms ACCESS point and ACCESS layer switch. They have different meanings. An Access Layer switch is a switch that resides on the access layer of the three tier network design model: Core, Distribution and Access. The access layer of this model is the portion of the network that connects to the end devices such as phones, PCs, access points and so on. (For more information about the three tier network design model, take a look at this link: http://www.cisco.com/web/learning/netacad/demos/CCNP1v30/ch1/1_1_1/index.html)

The main purpose of the Access Layer switches as far as the access points are concerned is to provide network connectivity to the enterprise network. Additional features that these switches provide for the access points are:

  1. Power over Ethernet to power the access points via the Ethernet cabling, so no mains or power supply is needed where the APs are being installed.
  2. Separation of each SSID into a separate VLAN
  3. QoS and port security features.

For the most part, these additional features are available not only to Access points but to all devices connecting to the Access Layer switches.

I hope this has been helpful!

Laz

6

Hello Rene,

Could you please let me know what is your suggestion for a good book for wireless (Beginner to intermediate level)? Thanks in advance.

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Hi Wisam,

I can highly recommend all the CWNP material. CWNA is the “beginners” material. Take a look at this book:

CWNA: Certified Wireless Network Administrator Official Study Guide

It’s vendor neutral and explains all the L1/L2 wireless stuff in detail.

8

Thanks Rene,
I got it 2 days ago and it’s really good book.

Thanks a lot again Rene!

1 Like
9

Good to hear you like it!

If you want to look at wireless frames, keep in mind that Wireshark on Windows doesn’t show 802.11 frames. Most windows drivers for wireless adapters don’t support “monitor mode”. If you want to look at 802.11 frames, the best thing to do is to download Kali and use one of the supported wireless adapters:

http://www.wirelesshack.org/best-kali-linux-compatible-usb-adapter-dongles-2016.html

These support client mode, monitor mode but also packet injection which is great if you are diving into WEP/WPA(2) security and other wireless attacks.

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could it be provisioned in collapsed core model too ?

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Hello Juan.

Yes it could. The underlying physical architecture of the wired network is for the most part independant from the creation of CAPWAP tunnels and the provisioning of LWAP devices. That is the case as long as the network has been configured appropriately for the amount of traffic that is expected. What’s important for the CAPWAP tunnels is that the VLANs are configured correctly in the network so that the tunnels can form.

I hope this has been helpful!

Laz

12

Hello,
I hope you are well.
Rene,
I would like to know what image you used to make the laboratories that involve not only the WLC but also the AP.
In the eve-ng emulator I can’t add an image to emulate the AP, how do I do it?
Please help me.

Greetings,

13

Hello @nevescutambo ,

I used a physical WLC 2504 and physical AP for my examples. Cisco has a Cisco Virtual Wireless Controller but there aren’t any virtual APs.

Rene

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14

Hi guys,

I just read lesson “Introduction to Wireless LAN”, and I thought confusing the way you introduced roaming vs. LWAPP vs. CAPWAP (just my opinion, fell free to disagree).

When I read the lesson, it sounded like: “Hey, we use roaming ONLY in large enterprise networks, and there is ONLY a single way to implement roaming, which is using LWAPP / CAPWAP protocols (and a WLC controller)”.

I know that this is not what you are trying to say.

We can use roaming without a WLC controller in a small network (like a small local home network with 2 APs), and we are not required to use a WLC controller, since we can just use 2 APs with same SSIDs and same security settings. Note: I’m aware that this solution has limitations, like handoff latency, disconnection due to MAC address caching in switches, or that it just works with pre-shared key auth (not viable for Enterprise level authentication). Note2: More about the MAC address caching problem in switches during roaming, and solutions: ex: https://www.reddit.com/r/ccnp/comments/cfit3k/layer_2_mac_address_tables_80211r_roaming_question/, https://www.reddit.com/r/ccnp/comments/cfit3k/comment/eub1esg/.

I think you were just trying to say that, in large networks, we need better solutions to get seamless roaming, and that LWAPP / CAPWAP with a WLC is the usual solution for this case.

However, imagine a new student that never studied about Wifi and roaming before, and just reads the lesson. I’m afraid that the student will think LWAPP / CAPWAP / WLC is the ONLY possible approach.

The solution I propose is: add a new session, like “Roaming in small networks”, where you introduce roaming, and provide an example of roaming between 2 APs into a small home.

Then, in session “Enterprise Wireless LAN”, you may explain that for larger networks when we need a different approach, since previous approach has limitations and doesn’t scale, and then introduce LWAPP / CAPWAP / WLC.

Update: You provided a much better explanation about roaming in the next lesson, “https://networklessons.com/cisco/ccna-200-301/wireless-lan-802-11-service-sets”, at session “Extended Service Set (ESS)”. So here I think it’s just a matter or order: when you talked about roaming / enterprise networks / LWAPP / CAPWAP / WLC, everything together, before explaining roaming / SSID / BSSID / ESS, so things get confused. Again, I think quickly introducing roaming into a small home w/ 2 APs scenario before moving to the more complicated LWAPP / CAPWAP solution will clarify better the lesson.

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Hello Rarylson

Thanks for your feedback, it’s always helpful for us to get such information to help improve lessons and to become an even better site for all of our users!

I think the issue you bring up is a good one, and it is important to be very clear. I think in this case, we need a clarification of specific terms. It depends upon your definition of roaming. The term is often used loosely for various things.

Strictly speaking, roaming is what happens when a wireless client disconnects from one access point and connects to another as the client physically moves from the range of the first to the range of the second. But roaming also includes the mechanisms that make that handoff seamless. That means that any communication taking place, such as a video conversation, for example, will experience no discontinuity during the handoff. That requires specific mechanisms that can only be delivered using a WLC.

Simply moving from one access point to another with the same SSID in a home environment is not considered roaming, with the strict definition that we have established above. However, because the term is often used loosely, as I said, based on context, we can use the word roaming to describe such a situation as well. However, those mechanisms that deliver seamless handoff are not present in such a situation.

Now having said all that, it looks like Rene used the strict definition in his Introduction to Wirelesss LAN lesson, and the loose definition in his Service Sets lesson. Based on context, I believe his hope was that this was clear.

However, I will share this info with Rene and have him look over the content to make any necessary changes he sees fit.

Thanks again for your feedback, it’s invaluable!

I hope this has been helpful!

Laz

16

Your response was very clear and helpful. For sure it will also provide clarification to anyone else that has the same doubt in the forum.

But I still think you could add to the lesson the loose definition of roaming, using the example of a small home with 2 APs, and explaining that it’s a simpler implementation that has limitations and is not seamless.

Then in the next part, explain that in large enterprise networks and when we have seamless requirements, that approach doesn’t work, then introduce the strict definition of roaming (seamless roaming), and the implementation via WLC.

Does it make sense?

17

Hello Rarylson

Thanks again for your feedback! I will forward this information to @ReneMolenaar to take a look and make any improvements that may be necessary.

Thanks again! :sunglasses:

Laz

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Wireless Networks Basics:
I would like to understand the following topics better. When we talk about wireless networks and the standards and technologies used, I seem to get a bit confused with some of the basic aspects in wireless networking. So I would like to clarify the same. Thank You for taking the time to go through my questions and answering them.

  1. What is a Wireless channel? For example, we say 802.11a uses 23 channels on a 5GHz frequency.
    So what does it mean?
  2. When we create multiple SSID’s on a wireless router, are we creating multiple wireless networks?
    Now if we create a wireless networks that connect my Printer, TV and smartphones and separate it from a Guest Network, can applications like whatsapp on mobiles connected to 2 different wireless networks interact with each other? Since Guest networks also have access to Internet, I am assuming these 2 devices on different wireless networks can get their messages delivered?
  3. With a wireless LAN Controller, does an access point forward all traffic to another access point when a device is roaming? Assuming that the authentication details of the client are shared between access points by the LAN controller?
    Also, does the traffic from one AP to another ap get routed via the WLC ?
  4. Creating 5 SSID’s on my wireless router is similar to Creating an unique SSID for 5 different physical wireless routers?
    Wireless
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Hello Adhithya

I will do my best to answer your questions.

Take a look at the following two NetworkLessons notes on the topic of 2.4 GHz and 5 GHz frequency bands and channels:

Yes. Essentially, in the same way that a VLAN corresponds to a single broadcast domain/network segment/subnet, when you create an SSID on a wireless AP, you are essentially creating a wireless broadcast domain/network segment/subnet. Typically each SSID will correspond to a different IP addressing subnet, thus if you connect your TV to SSID1 and your smartphone to SSID2, they wouldn’t be able to communicate with each other unless you have configured routing somewhere on the network. Just like if two PCs were connected to two different VLANs, they wouldn’t be able to communicate unless routing was configure to route traffic between the subnets.

A WLC manages the APs in a network. When a device roams from one AP to another, the WLC helps to facilitate a smooth transition. ΅When roaming, the AP doesn’t forward all traffic to another AP, but the device will switch to a new AP based on signal strength and other factors. The WLC is involved in the process, but traffic doesn’t necessarily route through the WLC, it depends on the network design. Take a look at the following for more information:

Yes. Functionally it is exactly the same from the point of view of the wireless clients. This would create 5 separate broadcast domains/network segments/subnets. However, the difference is that these 5 SSIDs would all share the same physical hardware i.e. the wireless router. This can be a limiting factor when it comes to the number of clients you would be able to support.

I hope this has been helpful!

Laz

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Thank You @lagapidis!! I am going to give Wireless networks another read. Appreciate you taking the time to respond to my queries. Thanks again.

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