## Pi Zero add to /etc/dhcpcd.conf

profile fb_usb0
static ip_address=172.19.180.1/24
static routers=172.19.180.254
static domain_name_servers=8.8.8.8 208.67.222.222

interface usb0
fallback fb_usb0

## Pi3 add to /etc/dhcpcd.conf

profile fb_usb0
static ip_address=172.19.180.254/24

interface usb0
fallback fb_usb0

## Pi 3 setup NAT

sudo sh -c "echo 'net.ipv4.ip_forward=1' >> /etc/sysctl.conf"
sudo sysctl -p /etc/sysctl.conf

sudo iptables -t nat -A POSTROUTING -s 172.19.180.0/24 ! -o usb0 -j MASQUERADE
sudo iptables -A FORWARD -i usb0 ! -o brint -j ACCEPT
sudo iptables -A FORWARD -o usb0 -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
sudo sh -c "iptables-save > /etc/iptables/rules.v4"