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Archive for August 2013

Why spectrum analyzers are still relevant.

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Wireless networks have seen many different trends emerging over the years, probably one of the most prevalent trend is the ability for access points to monitor to the RF spectrum around the access point. Whether you work with Cisco CleanAir, Aerohive, Aruba, or one of the other big wireless vendors they each have their own way of monitoring and reporting the surrounding RF environment. This is definitely a feature that is very useful for viewing the overall health of the wireless spectrum, after all this spectrum is the layer 1 medium for the WLAN and if there is a lot of contention/interference over the RF then the WLAN will see a performance degradation.

One thing I have inadvertently seen this built-in feature do is provide a false sense of security and make people believe they do not have a need to have any other spectrum analysis tool. There is one flaw with relying on this feature, it is the fact that this feature will only provide you a view of the RF surrounding the access point, while your first reaction is going to “well yes it does, that is what it is supposed to do” this feature does not (and will not) provide you with a view of the spectrum from the client’s perspective. Consider a deployment where you do not have access points peppered around an area every 20 feet and instead have access point spread out every 50-80 feet and you hear consistent complaints of wireless issues. The first reaction of any network engineer is going to be check the access point:

  • Is the access point servicing clients
  • Is there a configuration issue
  • How does surrounding RF look
  • What do the wireless statistics look like

Now usually one of those four things will point you in the right direction, but what I find that is pretty common trait is that after reviewing the RF statistics surrounding the access point (and assuming it looks good/normal) no further thought will be given to the layer 1 medium simply because they looked to access point. All the while the client wireless device might be a good 30 ft away behind a few obstacles surrounded by or near a set of interfering devices.  That is where you would want someone on the ground with a spectrum analyzer.

I’m not saying you need to have a spectrum analyzer everywhere you have wireless because we all know in large networks wireless can grow drastically and certain large networks can see thousands of access points across many different offices, but I merely want to point out a flaw in completely relying on a technology that provides RF Spectrum visibility from the access points perspective, because that is all it is.

Written by Stephen J. Occhiogrosso

August 28, 2013 at 11:42 AM

CWNA Check!

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Well, I finally got around to taking a shot at the CWNA exam and ended up with some successful results! It feels like an eternity but over 2 years ago I took a stab at CWNP’s CWTS exam. If you remember from my assessment of the CWTS exam itself I was able to knock it out fairly easy with a passing score in the 90’s with an ending statement that I should have just skipped the CWTS and went straight for the CWNA. Well after passing the CWNA with a score again in the mid-90’s I still stand by that statement. However I’m sure the additional 2 years of experience since then provided me with a considerable handicap.

In regards to my study preparation for the CWNA, just like I did for the CWTS I used official CWNP CWNA Study Guide from Sybex, that and the 6 years of wireless experience I have. Just like the CWTS exam I found the CWNA to be very straight forward it did have a lot of good questions that made me do a bit thinking and the questions were much more detailed then what I remember dealing with on the CWTS exam. This time however a quick read the through the CWNA study guide was pretty much all I did. I did utilize one or two of the question pools that are available for purchase on CWNP’s website and the questions are great for exam preparation if there is anything I commend CWNP for it is for providing great study material for thier exams.

Now, I still consider the CWNA should be basic knowledge for any network administrator/engineer that has to work with an extensive WLAN. After all everyone knows wireless is a bit more complicated then just deploy access point and hope for the best, having an understanding of the 802.11 technologies is detrimental to a successful WLAN deployment in my own opinion. Now while CWNA doesn’t cover all the 802.11 protocols in great detail I think it is a great entry point at understanding the technologies from a high level. Now, i just hope the CWNP certification gain a bit more traction in the job and because just as well as the CCNA/CCNP certification.

Written by Stephen J. Occhiogrosso

August 23, 2013 at 6:23 AM

Reconsidering the way we think about ‘virtualization’

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Ever so often I will see an article that discusses ‘how few people know about virtualization’ or ‘how many people do not run virtualized environments’ and I do have to admit a part of me shakes my head at these articles. Mainly because those articles (in my mind) do not properly describe the ‘virtualization’ they are trying to talk about. They simply mention the term ‘virtualization’ and continue on when the real fact of the matter is I’m sure 99% of us in the IT world are dealing with virtualization right and don’t even realize it.

Whenever people discuss virtualization it is typically going to involve VMWare, Hyper-V, or Citrix, however when you consider what virtualization really is, it has been around decades going back to Partitions on an AS400 midrange system. I’ve spent a fair amount of time thinking of a way summarize ‘virtualization’ and I think this one might have been one of the best

“Providing multiple services securely and isolated over the same physical hardware”

(There is probably a flaw in that statement but anyway) Now if we think about that for a minute and then think about network designs (Yes, I had to bring up network design, you knew this was going somewhere network related right?!) we virtualize our networks to an extent:

  • VLANs Virtual LAN – Providing multiple Local Area Networks over the same physical switch
  • VRF Virtual Routing Forwarding – Providing multiple routing instances within the same physical router. A layer 3 VLAN if you will.
  • VDC Virtual Device Context – Similar to VRF’s but for Nexus/Data Centers.

We even have virtual Wireless LAN Controllers, Virtual Firewalls, Virtual switches, and so forth

Now when you consider VLANs, VRF, & VDCs a virtualization technology I think almost everyone will attest to being a familiar with virtualization in one aspect or another. So I think it is time we stopped considering virtualization something new and something that is limited to ‘servers’ as it has really been with us for a while, we’ve just been abbreviating for years!

(That and the fact VMWare/Hyper-V have been out there for years now)

Written by Stephen J. Occhiogrosso

August 21, 2013 at 1:32 PM

Posted in Virtualization

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