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View Full Version : [ubuntu] Unable to get the specific AP info via "iwlist wlan0 scanning"



nakoruru
November 3rd, 2010, 11:41 AM
Hi, i have a router with wireless on,and i want to get the ap information via "iwlist wlan0 scanning",but seems the scan result does't contain the ap info i want. meanwhile, the cell phone can get the router ap info, does anyone encounter same questions? and how to resolve? i try to reboot the PC or router, but it doesn't work.

nakoruru
November 3rd, 2010, 01:18 PM
i got some new informations. but also got some new questions.

1.when the ap is in the 13 frequency band, i can't get the ap info via iwlist scanning. which is very weird.

2.Given that the i get the ap info of my router which is in frequency band 1, then i change the router to frequency band 13, but when i execute "iwlist wlan0 scanning" , i still find that the ap is in frequency 1. i guess the wifi doesn't "really" scan the ap around but instead,it just get the result from cache, if it's true, how to clean the cache and make the wifi do a "real" scanning.

grahammechanical
November 3rd, 2010, 01:24 PM
What particular information are you seeking? Are you looking for information about your own setup or about nearby wireless Access Points?

Check out the Wireless Trouble Shooting Guide at


https://help.unbuntu.com/community/WifiDocs/WirelessTroubleShootingGuideRegards

nakoruru
November 4th, 2010, 01:42 AM
thanks for your reply, i am seeking for the information about my own wireless setup to sovle the 2 weird issue:
1. unable to get the nearby ap info which is in 13 frequency band.
2. when a nearby ap change it's frequency band from other to 13, the ap is still found in it's original band by executing"iwlist scanning ", but actually unable to connect.

chili555
November 4th, 2010, 03:24 AM
i guess the wifi doesn't "really" scan the ap around but instead,it just get the result from cache, if it's true, how to clean the cache and make the wifi do a "real" scanning. Here is a quote from man iwlist:
Triggering scanning is a privileged operation (root only) and normal users can only read left-over scan results.The short answer is:
sudo iwlist wlan0 scan

nakoruru
November 4th, 2010, 04:27 AM
thanks chili555^^, but i do run the command as root, so i guess i actually get the latest ap info, and i also try "sudo iwlist wlan0 scanning", but get the same result:).

below is the detailed phenomenon:

first,i change the router to frequency band 6 (namely channel 6), and my wifi can find it and show that it is in frequency band 6, now i change the router to band 13(or 12), my wifi still find it , but it show that the route ap is still in band 6, this should be wrong. and after a period of time, the route ap info disappeared.
if i change the route to other band such as 1,or 9, wifi can discover the change immediately.

so i conclude that the wifi i used is unable to detect the ap info which in frequency band 12,13, and the wifi doesn't clean the ap info which is already unavailable in times.

any advices? thanks^^:guitar: