Site Survey Questions

[steelinquisitor]

Hello,

I have a question about surveying. I have been doing site surveys and all the site surveys that I have done were all passive mode. I use AirMagnet with Proxim card. I know that there is an active mode for doing wireless site survey. My question are:

1. When do I need to do an active site survey?

2. What is the difference between active and passive mode?

3. What is the advantages and disadvantages of each mode?

4. For post site survey, which mode should I used?

I know that the passive mode is in monitor mode and I don't need to associate with an AP whereas active mode I need to associate with the AP.

Thanks

[Stephen Rodriguez · Accepted solution]

Granted, this is My Opinion:

1. When do I need to do an active site survey?

     When you are troubleshooting an issue.  And/Or needing to do throughput testing, on a live network.

2. What is the difference between active and passive mode?

     Active survey's you are actually connecting to the SSID, so you can pass traffic and measure the results.

3. What is the advantages and disadvantages of each mode?

     Active Survey - Allows you to see more information on packet frames, as you are connected to the SSID.  You can watch and test roaming, throughput etc.

     Passive Survey - Is what you want to use when you are doing a pre-install survey, or even a post install validation survey.

HTH,
Steve

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[steelinquisitor]

Thanks for the quick reply Stephen.

Is it possible to use active site survey for pre-install?

If it is, why would I use active survey for pre-install?

I was playing with active site survey while I was waiting for a reply, and I noticed that it is very similar to passive. I can merged the data (per AP), etc.

Also, regarding active survey to see the packet frames, where should I see these packet frames in Airmagnet?

I have merged all the APs that I have on my test active survey file, and could not figure it out.

Thanks

[Stephen Rodriguez]

You can do an active survey for pre-install, I just don't see the point myself. When you just have an AP on a Stick, you're not passing any data to the LAN to be able to gather informaiton about retries, throughput etc.

I want to say it's in the Display area when you hover over the map.

HTH,
Steve

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[steelinquisitor]

I took some screenshots between the active and passive.

On the active site survey, the APs are connected to the network. the retry and lost are 0.

Active

Passive

[Scott Fella]

I agree with Steve.... we will only do an active survey if troubleshooting, but always have done passive. Even troubleshooting, I still use passive and active.

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[steelinquisitor]

It seems like I will be doing active survey for my site survey next week.

I am still trying to figure this out. I noticed that when doing active survey via SSID it only scans one channel. THerefore, if I need to do both 2.4GHz and 5GHz, I would need to walk twice. Am I right on this one?

I double checked my AP config and I have both 2.4GHz and 5GHz up/up. inSSIDer can see both bands, Airmagnet passive mode can too, but not in active mode.

[Scott Fella]

That is right unless you have multiple cards. How a true survey is performed using an active survey approach was to survey the floor in a certain direction, then survey the floor again going the opposite direction and then perform a passive survey and then merge the data. This is why we don't do active surveys these days.

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[steelinquisitor]

Scott thanks for explaining the old ways of surveying.

I have been surveying and for the past year and there is still too much info to learn.


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[Scott Fella]

There is a lot to learn, but the best way is to collaborate with others in your team that survey.  I always tell me peers that is better you you to perform a site survey and do the design and install and then a validation or post survey.  This way you will know if how you surveyed was ideal or not.  This is how you learn... from experience seeing the final product.  Office areas, warehouse, manufacturing, outdoor, freezers, stadiums, schools... are a different and survey technique will change in different environments.

Thanks,

Scott

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[steelinquisitor]

Scott or Stephen,

I'm just curious when you guys do your site surveys, what is your signal propagation settings?

[Scott Fella]

It varies depending on if your supporting data only, voice, location, byod etc. for data, -72 dbm and an snr of 20 dbm or better.

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