I have a droplet running strong swan VPN which I installed using this guide: https://www.digitalocean.com/community/tutorials/how-to-set-up-an-ikev2-vpn-server-with-strongswan-on-ubuntu-18-04-2. Everything works ok as I can telnet into the remote server with its private IP from the droplet running the strong swan VPN.
I have also set up the same droplet as the VPC gateway using this guide https://docs.digitalocean.com/products/networking/vpc/resources/droplet-as-gateway/
The issue I’m currently facing now is that I cannot telnet into the remote server from droplets that are in the same VPC as the VPN server. I think I would need to connect the droplets to the VPN server but I’m not sure how to go about that. Any help is appreciated.
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You will need to configure the iptables rules and enable IP forwarding on the VPN server.
First, enable IP forwarding by editing the /etc/sysctl.conf file and uncommenting or adding the following line:
net.ipv4.ip_forward=1
Apply the changes with the command:
- sudo sysctl -p
Next, set up iptables rules to forward traffic from your other droplets to the VPN server. Replace eth1 with your private network interface and eth0 with your public network interface:
- sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
- sudo iptables -A FORWARD -i eth1 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
- sudo iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT
Ensure that you save the iptables rules and configure them to persist across system reboots. You can follow the iptables guide on Ubuntu for more details.
If your droplets are not already in the same VPC as the VPN server, you can follow this guide on how to use VPCs with DigitalOcean.
For further information about configuring StrongSwan, consult the IKEv2 VPN Server Setup tutorial
Hope that this helps!
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