(BeagleBoneBlack)ubuntu@localhost:~$ sudo ifdown wlan0
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on LPF/wlan0/00:24:b2:3f:a1:e5
Sending on LPF/wlan0/00:24:b2:3f:a1:e5
Sending on Socket/fallback
(BeagleBoneBlack)ubuntu@localhost:~$ sudo ifup wlan0
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on LPF/wlan0/00:24:b2:3f:a1:e5
Sending on LPF/wlan0/00:24:b2:3f:a1:e5
Sending on Socket/fallback
DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3 (xid=0x540681cb)
receive_packet failed on wlan0: Network is down