WiFi - How to know supported channels by a wireless client by Ulises Cázares

 Hi, in this post I would tell you how to be sure which WiFi channels are supported by a wireless client so we can configure wireless solutions that will work with the endpoints in the environment.

I normally approach this topic in 2 ways

1. Directly in the wireless client

This one is the obvious option but, in my experience, the majority of wireless clients don't show that in any part of the configuration. Because wireless clients are very different and their configurations menus too there's no way to show a "common" path to see the supported channels(if the wireless client shows them)

 
2.- Use a wireless adapter in monitor mode and wireshark to see an Association Request paquet from the client. In the following images we'll see where in the association request we can see that information. 

 

The fastest way to do it is to follow these steps:

• Put the wireless adapatar in monitor mode in the AP channel we'are going to connect the wireless client
• Open wireshark to see packect of the wlan adapter, for explae: wlan0
• Write the wireless client's MAC address so we know the packet is from the endpoint we want. In this case, my wireless client MAC is: 14:18:c3:89:35:a5
  
• set the filter wlan.fc.type_subtype == 0   (0 means association request)
• Once a packet is capture, open the packet int he following section:
• IEEE 802.11 Wireless Management
• Tagged Parameters
• Tag: Supported channels
• 

With this information, we can setup the wireless solution in order to use only the channels our wireless clients use to avoid roaming and/or disconnection issues.

Hope this helps