Question

Route all OpenVPN connections through Floating IP

Posted on October 9, 2018
VPN Debian
Asked by itai

I used this tutorial to setup an OpenVPN server on a Debian droplet: https://github.com/Nyr/openvpn-install I’ve also added a floating IP to the droplet, and now I’d like all connections to the VPN to appear as if they are coming from the floating IP, and NOT the primary IP of the server

When SSHing into the server, I managed to use the floating IP with a curl call:

curl --interface [ACNHOR-IP] https://api.ipify.org/

This worked - it gave the floating IP as response

How can it be done? I saw this tutorial, but not sure what are the correct values, since the netstat -anr doesn’t give a similar output (I have only one record: eth0 )

Thanks in advance

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Alex • October 10, 2018

Accepted Answer

I managed to get both incoming connection and outgoing to occur via the floating ip. In /etc/openvpn/server.conf i added a line local floating-local-ip(10.19.0.6) after which i restarted openvpn with service openvpn restart. After that i have removed/added some iptables rules like below:

iptables -t nat -D POSTROUTING -s 10.8.0.0/24 ! -d 10.8.0.0/24 -j SNAT --to-source droplet-ip
iptables -t nat -D POSTROUTING -s 10.0.0.2/32 -o eth0 -j SNAT --to-source 10.19.0.6
iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE
iptables-save

root@ghost-s-1vcpu-1gb-fra1-01:~# netstat -anr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         165.227.144.1   0.0.0.0         UG        0 0          0 eth0
10.8.0.0        0.0.0.0         255.255.255.0   U         0 0          0 tun0
10.19.0.0       0.0.0.0         255.255.0.0     U         0 0          0 eth0
165.227.144.0   0.0.0.0         255.255.240.0   U         0 0          0 eth0
root@ghost-s-1vcpu-1gb-fra1-01:~# netstat -ltnup | grep 1194
udp    12288      0 10.19.0.6:1194          0.0.0.0:*                           829/openvpn
root@ghost-s-1vcpu-1gb-fra1-01:~#

In my user.ovpn i have replaced remote droplet-ip 1194 with remote floating-ip 1194

All of the above was on a clean Ubuntu 18.04 install.

raymoncada • March 8, 2019

This is the answer you are looking for: https://blog.programster.org/openvpn-digitalocean-ip-alias

Alex • October 9, 2018

Heya,

Maybe this will help you with your task.