BBB File /etc/udhcpd.conf

This file determines what addresses are issued when the WiFi is operating in AP mode (client mode doesn't need a DHCP server).

If the BBB is plugged into a wired network (which will only occur at home), then the subnet/router/dns options come into play. If the BBB is acting as a standalone AP, they're inert.

The comment stuff is when the USB Gadget thing is operational. Since that's compiled out of my kernel, it's not applicable.

#start      192.168.7.1
#end        192.168.7.1
#interface  usb0
#max_leases 1
#option subnet 255.255.255.252

start      192.168.17.2
end        192.168.17.254
interface  wlan0
option subnet 255.255.255.0
option router 172.16.0.128
option dns 172.16.0.1