source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback

# LAN network interface
# Alternate access
# Set UP by default at boot whatever it is connected or not
# Will be set DOWN when WLAN will come UP
# Will be set UP   when WLAN will come DOWN
auto usb0
iface usb0 inet static
    address 192.168.0.250
    netmask 255.255.255.0
    network 192.168.0.1
    dns-nameservers 192.168.0.1

# WLAN network interface
# Main access - Default gateway
# Hotplug managed
# Will set LAN DOWN after it comes UP
# Will set LAN UP   when  it will come DOWN
allow-hotplug wlan0
iface wlan0 inet static
    address 192.168.1.250
    netmask 255.255.255.0
    network 192.168.1.1
    gateway 192.168.1.1
    dns-nameservers 192.168.1.1
    wireless_essid 'xxxx'
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
   #up   /sbin/ifdown usb0
   #down /sbin/ifup   usb0
