Wireless scan won't show one network

navaneethkn · 2012-02-26 07:05:23

I have a weird problem of connecting to a wireless network. I am connecting to a network named "C-202" with WPA-Personal. This network shows up in the scan results some time and won't show some time. I can't really figure out a pattern from this. Sometime the network won't show up. It may work after few restarts.

I was using Wicd initially and thought this was the problem with wicd. Uninstalled wicd and started using NetworkManager, but the problem persists. Then I tried the scan directly on terminal like

sudo iwlist wlan0 scan

This shows a list of networks available, but not the one I want to connect. I can connect to that network from other computers, but not from this.

Interestingly, when I change the SSID from C-202 to C-202-New, it shows up in the list and I can connect. The connection works for few days and the problem starts again. Changing the SSID again will fix it. It looks to me like some cache is messing things up.

I have no clue on how to debug this issue. Can anyone help me to debug and fix this issue?

Any help would be appreciated

t1nk3r3r · 2012-02-26 10:45:19

Is the AP hidden? Write down the MAC address and search the scan results. I've had mixed success with hidden APs, but they still show up on a scan as ESSID=""
Another possibility is a crowded frequency. What channel are neighboring APs on?
And always check signal strength with 'iwconfig' once connected. It's amazing how easily range can be reduced by interference.
It could be a driver bug, but we try to save that conclusion for last.

Maki · 2012-02-26 10:50:01

How far are the access point?, that might be the problem

navaneethkn · 2012-02-26 17:23:07

Hello,

Thanks for replying. AP is not hidden. Access point is very close and I am getting some 70% signal strength.

To debug the issue, I changed the SSID to 'C-2022' and scanned. It showed up. Now changed the SSID back to 'C-202' and scanned again. It is lost from the results. Which means, the name is cached somewhere and ignored for some unknown reason while scanning. Will iwlist cache something which is causing this issue?

Thanks in advance for any help.

olivierk · 2012-02-28 02:01:07

Exactely the same thing here, with ath9k.

navaneethkn · 2012-02-29 06:04:01

I got the following output from "lspci | grep -i net"

02:00.0 Ethernet controller: Broadcom Corporation NetLink BCM5787M Gigabit Ethernet PCI Express (rev 02)
03:00.0 Network controller: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection (rev 02)

I think the driver for this card is iwl3945. "lsmod" shows the module is loaded.

iwl3945 71099 0

I am wondering if this is happening because I am using a wrong driver?

@olivierk - Thank you for confirming you have the same issue. I don't think it is an issue with ath9k because I am not using ath9k but still has the problem. Have you got a solution?

Any help would be great!

t1nk3r3r · 2012-02-29 06:51:48

You say you can connect from other computers...how? Are they wireless as well? Are they using similar hardware? And they are successfully connecting when this card is not?

If anything is keeping a cache, it should be Wicd or NetworkManager. However, 'iwlist wlan0 scan' reads signals fresh each time it is run. I don't think any cache is at fault.

The module corresponds to the lspci entry, no problem there.

How many other APs are there?

Have you noticed times of day/days of the week this is happening?

Is your card using powersaving features?

Arch Linux

#1 2012-02-26 07:05:23

Wireless scan won't show one network

#2 2012-02-26 10:45:19

Re: Wireless scan won't show one network

#3 2012-02-26 10:50:01

Re: Wireless scan won't show one network

#4 2012-02-26 17:23:07

Re: Wireless scan won't show one network

#5 2012-02-28 02:01:07

Re: Wireless scan won't show one network

#6 2012-02-29 06:04:01

Re: Wireless scan won't show one network

#7 2012-02-29 06:51:48

Re: Wireless scan won't show one network

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