Digital Ocean floating IP gateway script (force droplet to use the assigned floating IP for outbound traffic as well as inbound traffic)

floating-ip-gateway.sh

#!/bin/bash
# Force outbound traffic through the attached floating IP

NET_INT="eth0"
CURL_TIMEOUT=3

echo -n "Setting floating IP as the default gateway: "

# Check there's a floating IP attached to this droplet
if [ "$(curl -s --connect-timeout $CURL_TIMEOUT http://169.254.169.254/metadata/v1/floating_ip/ipv4/active)" != "true" ]; then
        echo "Error: this droplet doesn't have a floating IP assigned to it."
        exit 1
fi

# Get the gateway IP for the floating IP
GATEWAY_IP=$(curl -s --connect-timeout $CURL_TIMEOUT http://169.254.169.254/metadata/v1/interfaces/public/0/anchor_ipv4/gateway)

if [ -z "$GATEWAY_IP" ]; then
        echo "Error: failed getting gateway IP for this droplet."
        exit 1
fi

# Check we haven't already got the floating IP as a default gateway
if [ ! -z $(ip route ls 0/0|awk '{print $3}'|grep "$GATEWAY_IP") ]; then
        echo "Error: gateway IP already a default route."
        exit 1
fi

# Add the new route before we remove any
sudo route add default gw $GATEWAY_IP $NET_INT

# Delete any other default gatways for this interface
ip route ls 0/0 dev $NET_INT|awk '{print $3}'|grep -v "$GATEWAY_IP"|xargs -n1 -I{} sudo route del default gw {}

echo "Done."

It does create issues with the do-agent monitoring agent, which can be solved by adding a back a route for 169.254.169.254 via the original gateway :

ip route add 169.254.169.254 via [original_gateway_ip] dev eth0

After running this script my ssh session is frozen and I cannot access server via static ip. Also my domains that should resolve to static ip doesn't work. So seems inbound traffic is also affected. Or I'm doing it wrong?

@slonia Did you check your firewall settings? And try to use new ip address when connecting to server with SSH again.

@ufukty I'm looking for setup to make some app do requests from floating ip, while my static sites and other apps are using static ip

epic, thank you