Routing traffic through another droplet (on DigitalOcean.com)

route-traffic-through-droplet.sh

# on router / gateway
# https://serverfault.com/questions/306024/how-to-route-network-traffic-of-a-host-via-another-host

##### ON GATEWAY ##############################

# test IP
curl ifconfig.me

# Enable NAT
echo '
net.ipv4.ip_forward=1' >> /etc/sysctl.conf
sysctl net.ipv4.ip_forward=1

# use Private Network (interface eth1)
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

##### ON NODE #################################

# test IP
curl ifconfig.me

# make sure eth1 is private network interface
GATEWAY_PRIVATE_IP=x.x.x.x  # This is PRIVATE IP  on same subnet, not public
ip route replace default via $GATEWAY_PRIVATE_IP dev eth1

# ssh connection will drop. public access is cut (not too sure why yet)

# use DO console to verify ip is showing gateway IP
curl ifconfig.me

##### ON GATEWAY ##############################
# ssh should work on node private IP

NODE_PRIVATE_IP=x.x.x.x  # This is PRIVATE IP  on same subnet, not public
ssh root@$NODE_PRIVATE_IP