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Old 04-09-2016, 12:38 AM   #1
julianvb
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Ubuntu 12.04: Iwlist Scan vs. Network Manager


2016-04-09

I recently switched my Verizon FiOS Internet service from 15/15 based on an Actiontek router to 25/25 based on a Quantum router and my remote computers' wifi performance has improved significantly in that I no longer experience any dropouts and wifi connections are established almost as soon as a computer is turned on.

But I am puzzled by the data I get from the 'iwlist scan' command and the graphical network manager as illustrated by my attached files. Network Manager tells me that my bit rate is a solid 72 Mb/s whereas the iwlist scan shows a range from 1 Mbps to only 54 Mbps when I use a wireless-N adapter. When I use a wireless-G adapter, the differences are even greater between the two tools.

I'll appreciate any help in reconciling their seeming discrepancies.

Julianvb
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Last edited by julianvb; 04-09-2016 at 04:48 AM. Reason: attempts to add images
 
Old 04-09-2016, 01:15 AM   #2
ferrari
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Well, the iwlist results just show the advertised/supported bit rates (for given wireless protocols), while NM is showing the current negotiated bitrate. You'd need to use iwconfig to get the current bitrate, signal level etc at any one time eg assuming wlan4
Code:
iwconfig wlan4
 
Old 04-09-2016, 04:48 AM   #3
julianvb
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ferrari,

Thanks so much for your helpful explanation. I normally use iwconfig to obtain wireless-network information and find that NM and iwconfig always produce consistent information. In both the present wireless-N and wireless-G cases, both NM and iwconfig report identical bit rates of 72 Mpbs and 48 Mpbs respectively.

I delved into 'iwlist scan' yesterday only after I saw a demo of it at a Linux meeting. I guess its usage is limited in my daily Linux matters.

Julianvb

Last edited by julianvb; 04-09-2016 at 04:52 AM.
 
Old 04-09-2016, 05:07 AM   #4
ferrari
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Yes, it's more just for identifying AP's in range and providing information about them

From the iwlist manpage
Quote:
scan[ning]
Give the list of Access Points and Ad-Hoc cells in range, and optionally a whole bunch of information about them (ESSID, Quality, Frequency, Mode...). The type of information returned depends on what the card supports.
Triggering scanning is a privileged operation (root only) and normal users can only read left-over scan results. By default, the way scanning is done (the scope of the scan) is dependant on the card and card settings.
This command take optional arguments, however most drivers will ignore those. The option essid is used to specify a scan on a specific ESSID. The option last do not trigger a scan and read left-over scan results.
 
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Old 04-09-2016, 07:15 PM   #5
julianvb
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ferrari,

I've just installed Wavemon via Unbuntu's Software Center. You may have used it. I think it's concise, accurate and extremely user-friendly. To invoke it, I simply enter
Code:
wavemon
.

Julianvb
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Last edited by julianvb; 04-09-2016 at 07:37 PM.
 
Old 04-10-2016, 12:24 AM   #6
ferrari
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No, never used it. Network Manager is all I use. (Well, that and the standard CLI utilities.)
 
  


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