"Before capturing packets, configure WireShark to interface with
an 802.11 client device; otherwise, you'll get an alert "No capture
interface selected!" when starting a packet capture. To select an
interface, click the Capture menu, choose Options, and select the
appropriate interface. Be certain to monitor the correct RF
channel. For example, if the wireless network is set to channel 1
for the traffic you’re interested in, then configure
WireShark to monitor channel 1. To do this, click the Capture menu,
choose Options, and click Wireless Settings. The menu Advanced
Wireless Settings will appear where you can change the channel.
"Consider filtering the packet capture to reduce clutter when
analyzing packet traces. For example, you may be troubleshooting a
particular client device connecting to the network. In this case,
you can set a filter that excludes all packets except those
associated with the IP address of the client you’re
troubleshooting. To set a filter, click the Capture menu, choose
Options, and click WireShark: Capture Filter will appear where you
can set various filters."
