Create an IPSec Tunnel between a VDC and On-Premises Gateway

Introduction

This tutorial demonstrates configuring an IPSec site-to-site VPN Gateway for secure and encrypted communications, establishing a connection between an IONOS Cloud VDC and a simulated user-managed on-premises installation. It utilizes a managed VPN Gateway in the IONOS Cloud and a user-managed on-premises gateway.

Overview

This tutorial demonstrates the use of the following:

Before you begin

The following information is necessary to set up an IPSec connection between a VDC and on-premises VDC:

Reserve IP addresses

Before proceeding, ensure you have an IP block with at least one free IP address to assign to each gateway. For more information, see Reserve an IPv4 Address.

Configure LAN

This tutorial uses 192.10.1.0/24 and 192.10.2.0/24 for private LANs in IONOS Cloud (Left) and User On-Premises (Right) respectively. Remember to assign an IP address from the subnet to each gateway. The chosen IP address must be outside the DHCP pool and range from .2 to .9.

Generate Pre-Shared Key (PSK)

Our current IPSec implementation supports PSK (which is expected to support certificates in the future). When provisioning gateways, ensure you generate a PSK at least 32 characters long. Optionally, you can also generate a PSK while creating an IPSec tunnel. The following commands explain how to generate PSK for Linux and Windows, respectively:

openssl rand -base64 48
head -c 32 /dev/urandom | base64 

[System.Convert]::ToBase64String((New-Object byte[] 32))| Set-Content -Path .\psk.txt -Encoding ASCII

Execution

The execution process is divided into the following steps:

1. Simulate IONOS Cloud

2. Simulate on-premises setup

3. Provision the VPN Gateway

4. Configure the VPN tunnel

5. Deploy on-premises IPSec instance

6. Configure routing on LAN hosts

1. Simulate IONOS Cloud

Below are some screenshots from the DCD that contains the required VDCs.

To begin with, two virtual servers on the IONOS Cloud are provisioned and connected to each other via a private LAN. In this instance, LAN1 uses a custom subnet of 192.10.1.0/24. We designate these two servers as 192.10.1.10 and 192.10.1.11, respectively.

2. Simulate on-premises setup

Imagine the gb/ldn VDC as a user-managed site where you provision two virtual servers. Here, we will use the subnet 192.10.2.0/24. Host 1 has been configured with internet access (IP address: 203.0.113.20) and will function as the on-premises host acting as a user-managed gateway. We address these two servers as 192.10.2.2 and 192.10.2.3, respectively.

3. Provision the VPN Gateway

1. In the DCD, go to Menu > Network > VPN Gateway under Connectivity.

2. Click Create VPN Gateway from the VPN Gateways window.

3. Enter the following details:

3.1 Properties

3.2 VPN Tier

The Enhanced VPN tier is selected by default. The number of LANs and tunnels or peers differ for each tier. You can also enable High Availability for a chosen tier, allowing VMs to operate in an active-passive mode. It minimizes downtime during a failover and ensures an uninterrupted connection.

3.3 Protocol

The IPSec protocol is selected by default, and no additional configuration parameters are necessary.

3.4 LAN Connections

Attach a VPN Gateway to LANs in IONOS Cloud. You can only connect to LANs in the exact location where the VPN Gateway was provisioned. Take a look at the following mandatory parameters:

After selecting a data center, click Add LAN Connection to launch an additional pop-up window to set the following properties:

1. Click Save and wait for the gateway to complete provisioning. The process typically takes about 8-10 minutes, but further operations on the gateway will be instantaneous.

4. Configure the VPN tunnel

Now that the VPN Gateway instance is provisioned, the next step is to configure a tunnel to permit the two sides to talk to each other. We will need to configure a tunnel on both gateways, but the on-premises will be configured using IPSec configuration files.

1. Click Create Tunnels to begin configuring a new tunnel.

4.1 Properties

Enter the following details to configure a tunnel:

4.2 Authentication

Set the PSK as shown:

4.3 Initial Exchange (IKE_SA_INIT) Settings

Here, you can set the various encryption and integrity algorithms, Diffie-Hellman Group, and lifetimes for the IKE exchange phase. For demonstration, the available options are aligned with BSI best practices. However, we will accept the default selections.

4.4 Child SA/IPSec SA Settings (ESP)

Here, you can set the various encryption and integrity algorithms, Diffie-Hellman Group, and lifetimes for the ESP phase. For demonstration, the available options are aligned with BSI best practices. However, we will accept the default selections.

4.5. Network CIDRs

Configure the subnets in CIDR format, which are permitted to connect to the tunnel.

1. Click Save to save the tunnel configuration. This operation usually takes about one to two minutes to complete.

5. Deploy on-premises IPSec instance

In this tutorial, Host 1 in gb/ldn acts as a user-managed gateway. The host has internet access, so SSH can be used instead of the web console. Start establishing an SSH connection to Host 1's public IPv4 address in London.

apt-get update
apt install strongswan strongswan-pki libcharon-extra-plugins libcharon-extauth-plugins libstrongswan-extra-plugins libtss2-tcti-tabrmd0 -y

sysctl -w net.ipv4.ip_forward=1

203.0.113.10 203.0.113.20 : PSK "vPabcdefg123435hij565k7lmno8pq="

config setup
    charondebug=all
    uniqueids=yes
 
conn ionos-cloud-de-txl-demo
    type=tunnel
    auto=start
    keyexchange=ikev2
    authby=secret
    left=203.0.113.20
    leftsubnet=192.10.2.0/24
    right=203.0.113.10
    rightsubnet=192.10.1.0/24
    ike=aes128ctr-sha256-modp3072
    esp=aes128ctr-sha256-modp3072
    aggressive=no
    keyingtries=%forever
    ikelifetime=86400s
    lifetime=3600s
    dpddelay=30s
    dpdtimeout=120s
    dpdaction=restart

systemctl enable ipsec
systemctl start ipsec

root@london-lan-host-1:/etc# ipsec status
Security Associations (1 up, 0 connecting):
d44-5c8-48-87-28f9[2]: ESTABLISHED 3 minutes ago, 203.0.113.20[203.0.113.20]...203.0.113.10[203.0.113.10]
d44-5c8-48-87-28f9{2}:  INSTALLED, TUNNEL, reqid 1, ESP SPIs: c8f59a5e_i caa486ae_o
d44-5c8-48-87-28f9{2}:   192.10.2.0/24 === 192.10.1.0/24

6. Configure routing on LAN hosts

Currently, it is impossible to automate the addition of routes to LAN hosts to route the required subnets over the VPN Gateway. In this section, we will manually add the required routes. Remember to add them to the LAN hosts in both the VDCs.

6.1 Configure de/txl route

Step 1: Establish a console session to the LAN host(s)

We will use the web console to test connectivity for the LAN hosts without internet access. Open a console session and ping the LAN address assigned to the VPN Gateway, 192.10.1.5. Begin by pinging the IP address.

ip route add 192.10.2.0/24 via 192.10.1.5

6.2 Set persistent routes

In the 6.1 Configure de/txl route section, we added routes that will not persist during a reboot. You must determine how to set persistent routes for your choice of operating system.

 
{{auto eth0 

iface eth0 inet static 

address 10.10.1.10 

netmask 255.255.255.0 

post-up ip route add 10.10.2.0/24 via 10.10.1.5}} 

6.3 Configure on-premises route

Step 1: Establish a console session to the LAN hosts

Currently, the only way to access the system is through the web console, as we did not provide internet access for the second LAN host in our on-premises setup. First, open a console session and test the connectivity to the LAN address assigned to the VPN Gateway. In this case, the address is 192.10.2.2 (which corresponds to LAN Host 1, the user-managed gateway). Let us begin by attempting to ping this IP address.

ip route add 192.10.1.0/24 via 192.10.2.2

Verify connectivity

You should now be able to ping hosts in the simulated on-premises setup in gb/ldn from cloud hosts in de/txl and vice-versa.

Summary

You have successfully configured a site-to-site VPN between the IONOS Cloud and a user-managed on-premises setup by utilizing a Managed VPN Gateway in the cloud and a user-managed on-premises gateway.