Turn on IP forwarding

echo "1" | sudo tee /proc/sys/net/ipv4/ip_forward

Add a routing rule for forwarding internet

If you want to forward traffic from ethernet

sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

If you want to forward traffic from antenna

sudo iptables -t nat -A POSTROUTING -o wlan1 -j MASQUERADE

Save the iptables rules

Install the iptables-persistent package

sudo apt-get install iptables-persistent

Using this command to give you root user privileges

sudo su

Type this command to save the rules

iptables-save > /etc/iptables/rules.v4