Cisco Wireless Lan viewable by some clients, but not others.

[elliott callaway]

Hey there folks,

So I have a strange issue. I have a Cisco 877W router that has been running flawlessly for nearly 2 years. During that time I've never had to manually reset the router, it has been more reliable than my ISP.

However one month ago I left my business for a week and came back to find that the WLAN was no longer visible from my laptop. I searched google, tech forums, and these forums for conclusive explanations as to what is happening but found nothing.

The main issue is an inability to see the network, old wireless devices that have been using the WLAN for a while have no trouble viewing the network or connecting to it.

However, any time a new device is brought in (Samsung Galaxy Tab, new Laptops, and new Desktops) the WLAN is not available.

I was able to make the device visible to my laptop by changing the country code on my network device to Region 1, but this is not an option for all devices or configurations.

I have changed the broadcast channels, shutting down the WLAN, configuring WLAN differently (through several different Security methods).

My separate access points are usually visible by all clients, (I use D-LINK wifi routers configured to AP mode throughout my facility) however the Cisco just doesn't like to be seen?

Hopefully somebody has some insight or clues as to why this is happening, it is not a big issue right now, but as we continue to expand our network it will become a serious issue.

Please help,

stumped

e.callaway

[Amjad Abdullah]

Hello Elliott:

I faced this issue once and I found later it was a part of the clients because they were doing filtering on WLANs and excluding the target SSID from being listed. I think however this is not your issue because you face that with all new clients.

I would like to check a few things:
- If you tried to manually configure the SSID settings on one client that does not see the WLAN, will it be able to connect to it?

- Was there any chagne/moifications happened during your absence?

- Does the issue depend on how closer to the AP you are? or it does not matter if you are close or far from the AP?

You may collect wireless sniffer traces. The information in the management frames is supposed to tell us some information about the security features the AP provides and that may help us to find a clue.

If you don't have any utility to capture wireless 802.11 frames then please try the process on this link:

https://supportforums.cisco.com/docs/DOC-16398

Attach the file so someone check if if there is something intereseting.

HTH

Amjad

[elliott callaway]

Hello Amjad,

thank you for the quick reply.

Regarding your questions.

1. Manually creating the network on the clients does not allow for them to connect, they still see the network as OOR.

2. There were no changes at all to the network or the settings. I am the only one with root access into my network, and I am the only one who knows how it actually works. (Furthermore, worried that this may have been the case I reloaded both the standard LAN and WLAN config files I had saved for a rainy day).

3. Proximity to the device makes no difference whatsoever. My laptop (before I changed the region code) was tested at 40 meters (usually connects with 1-2 bars) 20 meters (edges of office areas) and at 1m still no change in availability,

I do not have a sniffer currently installed, I will go to your link and follow the steps listed. I did use a Radio Scanner on the Samsung Note but even the scanner could not pick it up (very strange).

I will use Netmon and see if I can get anything else.

Semi-on-topic...I had a similar issue 3 years ago with a Linksys home router I had purchased. It was available then became invisible to one specific client. (Ended up returning the router, but this is not an option here).

thanks again, and I will reply shortly with my findings.

elliott

[Amjad Abdullah]

Hello Elliott:

If you have some clients connecting and some can not that indicates that:

- The AP is working fine. It does it work by broadcasting the beacon frames. This is proven by some clients can see the signal and connect successfully.

- The reason why some clients do not see the signal is that there is some information in the beacon frames that freaks the clients out so they either consider the AP illegal to connect to OR they see they should not list it as available for whatever reason.

Because I never worked with the device model you mentioned, can you explain to me more points:

- Does your device support 802.11n?
- Does your device support both 2.4 and 5 GHz? If yes, does the problem appear with both frequency bands?

Thanks.

Amjad

[elliott callaway]

Yes, it is an 802.11 device, no it does not support 5GHz. (I have no clients that support 5G either).

Ran the MNM3.4, no data to capture from the wireless device.

[Amjad Abdullah]

Hi Elliott,

You need to configure the NetMon to sniff the channel your APs work at. It can be configured on a laptop to sniff the appropriate channel. If you are getting no data then you may have the Netmon not configure for the appropriate channel.
Note that Netmon does not show you the output when you capture. It just saves your capture into a file when it finishes. save the file and attach it. You can save the file in wireshark-compatible format.

[elliott callaway]

Saved the CAP data.  It looks like its telling me there are malformed packets.

Attaching the file here.

[Amjad Abdullah]

Malformed packets are ususlly due high interference or noise around. Do you have other wireless networks around? is there a metallic environment around?

What is the security you are using for the SSID xiorAP?

Why are you using channel 9? Can you try changing the channel to another channel (channel 1, 6 or 11)?

I can see some clients send broadcast probe requests but no one reply! maybe due the packet is malformed?

let me know if providing the above improved something.

Thanks.

Amjad

[elliott callaway]

Its funny you mention other networks because I removed one AP that had cross coverage with this specific access point.

I removed this maybe 3 weeks before the issue occured.

My facility is very large so I can be 99% certain there is no other radio interference in the area. I have done scans with my droid and there is far less interference here than say my apartment or other offices.

I have security set to open. But, I do all permissions on the router itself, only specified devices can obtain access, even though it is open connections can only be obtained once permissions are granted.

I was using channel 9 because it was the last one I stopped on when I was switching bands before. I switched to channel 1 and 11 just now with no different result.

I am going to try booting through different OS's to see if there is any difference here.

thanks for your time Amjad

e

[elliott callaway]

Just thought I'd drop in and give an update. I haven't fixed my issue per-se, but visibility has been restored to some clients.

I haven't made the network visible to all devices but Android devices seem to be able to see the network after extended periods of time at our facility.

I am still running tests with several different Linux distro's to see if there is any change. I should have an update regarding this within 3 days.

[Amjad Abdullah · Accepted solution]

Haven't you made any change so those devices start to see the WLAN after sometime?

[elliott callaway]

This apparently is an issue with Windows 7. On 3 Debian distro's of Linux the network was visible and connectable while Windows 7 could not from the same PC.

Windows Xp does not seem to have this issue either. I do not have Vista running anywhere so I cannot tell but I imagine it would be the same as 7.

The device (just one) which was able to see it after some time had no settings changes. It just sat around and eventually picked up the signal.

So I will attack this from the Windows side of things. Thanks for the replys and help Amjad. I will mark this as complete/amswered.

[Amjad Abdullah]

Thanks Elliott,

It could be windows-adapter compatibility. Try updaing the adapter's driver for windows 7 wireless card. That improves such situations usually.

Regards,

Amjad