Descubra o nome da interface, executando iwconfig
$ iwconfig
eth0 no wireless extensions.
lo no wireless extensions.
wlan0 IEEE 802.11bgn ESSID:"EvanCarroll"
Mode:Managed Frequency:2.437 GHz Access Point: D8:50:E6:44:B2:C8
Bit Rate=19.5 Mb/s Tx-Power=15 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Power Management:off
Link Quality=61/70 Signal level=-49 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:1 Invalid misc:80 Missed beacon:0
Nesse caso, é wlan0
e, em seguida, execute iwlist <interface> freq
$ iwlist wlan0 freq
wlan0 13 channels in total; available frequencies :
Channel 01 : 2.412 GHz
Channel 02 : 2.417 GHz
Channel 03 : 2.422 GHz
Channel 04 : 2.427 GHz
Channel 05 : 2.432 GHz
Channel 06 : 2.437 GHz
Channel 07 : 2.442 GHz
Channel 08 : 2.447 GHz
Channel 09 : 2.452 GHz
Channel 10 : 2.457 GHz
Channel 11 : 2.462 GHz
Channel 12 : 2.467 GHz
Channel 13 : 2.472 GHz
Current Frequency:2.437 GHz (Channel 6)
Nenhum desses canais está fora de 2,4 GHz. Não suporta 5 GHz.