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:
Components
Description
Two VDCs
- ionos-cloud-txl as IONOS's VDC.
- user-on-prem-lhr simulates a user-managed on-premises setup.
Managed gateways
We use a single managed gateway in ionos-cloud-txl for the cloud side.
For a user-managed gateway, we use on-premises simulation, install the components, and manually configure IPSec on a virtual server to complete the setup.
Architecture depicts IONOS Cloud and on-premises simulation connected over an IPSec tunnel
Before you begin
The following information is necessary to set up an IPSec connection between a VDC and on-premises VDC:
Components
IONOS Cloud (Left)(ionos-cloud-txl)
User On-Premises (Right)(user-on-prem-lhr)
VDC Name
ionos-cloud-txl
user-on-prem-lhr
Gateway Public Address
203.0.113.10
203.0.113.20
LAN ID
1
Not applicable
LAN Subnet
192.168.1.0/24
192.168.2.0/24
Gateway LAN Address
192.168.1.5
192.168.2.5
LAN Host 1
192.168.1.11
192.168.2.11
LAN Host 2
192.168.1.12
192.168.2.12
Pre-Shared Key
Remember to use the appropriate key.
Example:vPabcdefg123435hij565k7lmno8pq=. This is a sample key used as an example in this document. Do not use this key for real-world scenarios.
Note:
Ensure that the IONOS Cloud (Left) and User On-Premises (Right) LAN subnets are unique and do not overlap.
Using the same subnet CIDR in the IONOS Cloud (Left) or User On-Premises (Right) does not work. In such a scenario, we recommend either of the following options:
Move one of them to a different subnet.
Add an additional network connection to LAN hosts on one side using a unique subnet, and then route the unique subnet via the VPN Gateway.
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.
IONOS Cloud (Left) (ionos-cloud-txl) Gateway Public Address
User On-Premises (Right) (user-on-prem-lhr) Gateway Public Address
203.0.113.10
203.0.113.20
Configure LAN
This tutorial uses 192.168.1.0/24 and 192.168.2.0/24 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.
Components
IONOS Cloud (Left) (ionos-cloud-txl)
User On-Premises (Right) (user-on-prem-lhr)
LAN ID
1
Not applicable
LAN Subnet
192.168.1.0/24
192.168.2.0/24
Gateway LAN Address
192.168.1.5
192.168.2.5
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
The execution process is divided into the following steps:
Simulate IONOS Cloud
Simulate on-premises setup
Provision the VPN Gateway
Configure the VPN tunnel
Deploy on-premises IPSec instance
Configure routing on LAN hosts
1. Simulate IONOS Cloud (ionos-cloud-txl)
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 192.168.1.0/24. We designate these two servers as 192.168.1.11 and 192.168.1.12, respectively.
Configuration on IONOS Cloud
2. Simulate on-premises (user-on-prem-lhr) setup
Imagine the user-on-prem-lhr VDC as a user-managed site where you provision three virtual servers. Here, we will use the LAN subnet 192.168.2.0/24. The Users VPN GW has been configured with internet access (IP address: 203.0.113.20) and a private LAN address of 192.168.2.5, this will function as the on-premises host acting as a user-managed gateway. The two private LAN hosts are addressed as 192.168.2.11 and 192.168.2.12, respectively.
Configuration on a user-managed on-premises setup
3. Provision the VPN Gateway
1. In the DCD, go to Menu > Network Services > VPN Gateway.
2. Click Create VPN Gateway from the VPN Gateways window.
3. Enter the following details:
Components
Description
Example
Name
Enter a descriptive name for the gateway instance. It is not required to be globally unique but must be limited to 255 characters.
site_to_site
Description
Enter a descriptive text for the gateway. It is limited to 1024 characters.
VPN Gateway for creating an IPSec Tunnel between a VDC and on-premises gateway.
Location
Select a location from the drop-down list of available locations for VPN Gateway.
ionos-cloud-txl
IP Address
Select an IP address from the drop-down list of available public IPv4 addresses.
203.0.113.10
Define properties
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.
Note: You can only upgrade the tier or switch between High Availability (HA) and non-HA variants during editing.
Select a tier
The IPSec protocol is selected by default, and no additional configuration parameters are necessary.
Select a protocol
Attach a VPN Gateway to LANs in ionos-cloud-txl. You can only connect to LANs in the exact location where the VPN Gateway was provisioned. Take a look at the following mandatory parameters:
Components
Description
Example
Datacenter
Select a data center from the drop-down that lists VDCs in the same location as the gateway.
ionos-cloud-txl
Connections
A list of connected LANs and the LAN addresses.
Refer to the following table.
After selecting a data center, click Add LAN Connection to launch an additional pop-up window to set the following properties:
Components
Description
Example
LAN
The ID of the LAN to connect to.
1
IPv4 CIDR
The LAN IPv4 address assigned to the subnet's gateway in CIDR notation.
192.168.1.5
IPv6 CIDR
The LAN IPv6 address assigned to the subnet's gateway in CIDR notation.
Not applicable
LAN connections
4. 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.
Configure a tunnel
Enter the following details to configure a tunnel:
Components
Description
Example
Tunnel Name
Specify a name for the tunnel. It does not need to be globally unique and can be up to 255 characters long.
customer_site
Description
Enter more descriptive text for the peer, not exceeding 1024 characters.
Not applicable
Remote Host
The public IPv4 address of the remote VPN Gateway.
203.0.113.20
Configure tunnel properties
Set the PSK as shown:
Components
Description
Example
Pre-Shared Key
Enter a strong key that is at least 32 characters long.
vPabcdefg123435hij565k7lmno8pq=
Configure PSK
Note: Both sites typically have the same exchange settings. If the configuration differs on both sides, the two gateways will negotiate to agree on the most secure 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.
Components
Description
Example
Diffe-Hellman
The Diffie-Hellman (DH) key exchange algorithm makes a shared encryption key available to two entities without exchanging the key. The shared encryption key serves as a symmetric key for encrypting data. Only the two parties involved in the DH key exchange can derive the shared key, which is never transmitted over the network.
15-MODP3072
Encryption Algorithm
Encryption algorithms safeguard data to prevent third-party access during transmission.
AES128-CTR
Integrity Algorithm
Integrity algorithms verify messages and randomness, ensuring packets are authentic and not altered by a third party before arrival, and generate keying material for encryption.
SHA256
Lifetime
The duration (in seconds) for which a negotiated IKE SA key remains valid. Before the key lifetime expires, the SA must be re-keyed; otherwise, upon expiration, the SA must begin a new IKEv2 IKE SA re-key.
86400
Select a suitable algorithm
Note: Both sites typically have the same Encapsulating Security Payload (ESP) settings. If the configuration differs, the two gateways will negotiate to agree on the most secure settings.
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.
Components
Description
Example
Diffe-Hellman
The Diffie-Hellman (DH) key exchange algorithm is a method used to make a shared encryption key available to two entities without exchanging the key. The encryption key for the two devices is used as a symmetric key for encrypting data. Only the two parties involved in the DH key exchange can deduce the shared key, and the key is never sent over the wire.
15-MODP3072
Encryption Algorithm
Encryption algorithms safeguard data to prevent third-party access during transmission.
AES128-CTR
Integrity Algorithm
Integrity algorithms verify messages and randomness, ensuring packets are authentic and not altered by a third party before arrival, and generate keying material for encryption.
SHA256
Lifetime
The ESP SA specifies the duration for which keys generated during the IKE negotiation remain valid for encrypting and authenticating the data packets being transmitted.
3600
Select a suitable algorithm
Configure the subnets in CIDR format, which are permitted to connect to the tunnel.
Note:
You may use 0.0.0.0/0 to permit any network; however, one site should explicitly define the network CIDRs permitted. Using 0.0.0.0/0 on both VPN gateways will result in broken routing.
Components
Description
Example
Cloud Network CIDRs
Network addresses on the cloud side that are permitted to connect to the tunnel.
192.168.1.0/24
Peer Network CIDRs
Network addresses on the peer or remote side that are permitted to connect to the tunnel.
192.168.2.0/24
Configure network CIDRs
2. 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, Users VPN GW in user-on-prem-lhr acts as a user-managed gateway. It has internet access, so SSH can be used instead of the web console. Start establishing an SSH connection to Users VPN GW's public IPv4 address in London, remember to forward your ssh key when establishing this session. You will need this key while establishing a console session to the LAN hosts.
Deploy on-premises IPSec instance
5.1 Install pre-requisite software
Note: This tutorial performs a basic install and setup of Strongswan on Ubuntu. It is neither an in-depth guide nor does it contain detailed information about the configuration files' content. It is an exercise for the reader to determine the correct installation procedure for a secure production environment.
Update the package lists and install the required packages:
The VPN Gateway acts as a router and, therefore, is required to forward packets:
sysctl -w net.ipv4.ip_forward=1
This tutorial does not use an IPv6 address. If you intend to use one, ensure net.ipv6.config.all.forwarding=1 exists.
5.3 Configure IPSec
This tutorial will walk you through specific options for configuring IPSec, but the rest of the configuration remains an exercise for the reader. This section contains the configuration files and content specific to this installation and peer setup.
1. Populate secrets file
Currently, IPSec supports only pre-shared Keys (PSK), so ensure the /etc/ipsec.secrets file contains the key, so IPSec can read it from the file:
Next, populate the /etc/ipsec.conf file. This file contains a basic config setup section and a conn section that defines the configuration of the remote tunnel.
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 routing for IONOS Cloud LAN hosts (ionos-cloud-txl)
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, 192.168.1.5. Begin by pinging the IP address:
root@lanhost1:~# -c 3 192.168.1.5
PING 192.168.1.5 (192.168.1.5) 56(84) bytes of data.
64 bytes from 192.168.1.5 icmp_seq=1 ttl=64 time=0.456 ms
64 bytes from 192.168.1.5 icmp_seq=2 ttl=64 time=0.352 ms
64 bytes from 192.168.1.5 icmp_seq=3 ttl=64 time=0.503 ms
The LAN host(s) must know where to route the return traffic. To accomplish this, we will add a route for the user-on-prem-lhr LAN subnet (192.168.2.0/24) via the ionos-cloud-txl gateway's LAN address (192.168.1.5):
ip route add 192.168.2.0/24 via 192.168.1.5
We cannot ping hosts in the user-on-prem-lhr region because those servers do not yet know how to route the return traffic. To resolve this issue, continue adding routes for LAN hosts in user-on-prem-lhr.
6.2 Set persistent routes
In the 6.1 Configure routing for IONOS Cloud LAN hosts (ionos-cloud-txl) 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.
Persistent routes
First, add the configuration to your system's appropriate network or routing configuration files to set persistent routes. The exact method depends on your operating system. The following examples show how to make a route persistent across reboots for Debian, Ubuntu, CentOS, and RHEL.
Debian/Ubuntu
You can add the route to any of the following:
the /etc/network/interfaces file.
in a specific file under /etc/network/. Example: /etc/network/interfaces.d/.
use the ip route command in a startup script. Example: /etc/rc.local.
Example of /etc/network/interfaces:
{{auto eth0
iface eth0 inet static
address 192.168.1.11
netmask 255.255.255.0
post-up ip route add 192.168.2.0/24 via 192.168.1.5}}
CentOS/RHEL
You can add the route in /etc/sysconfig/network-scripts/route-eth0 and adjust it according to the relevant interface. Example: 192.168.2.0/24 via 192.168.1.5.
Save the configuration file changes and restart the network service to apply the changes.
6.3 Configure routing for on-premises LAN hosts (user-on-prem-lhr)
Note: Configure the host acting as a user-managed gateway, as it can already route traffic based on the IPSec configuration. This section focuses solely on the other on-premises hosts connected to the same LAN.
Step 1: Establish a console session to the LAN hosts
The user-managed gateway (user-on-prem-lhr) is connected to the internet and can be used as a jump-host to reach the on-premises LAN hosts. From the user-managed gateway, establish an SSH connection to the first LAN host (192.168.2.11), alternatively you may use the web console to login to the LAN hosts.
You can test the connectivity to the LAN address assigned to the user-managed gateway VPN Gateway (user-on-prem-lhr) using a console session. In this case, the user-managed gateway address is 192.168.2.5. Let us begin by attempting to ping this IP address.
root@users-vpn-gw# ssh 192.168.2.11
root@lanhost1# ping 192.168.2.5
PING 192.168.2.5 (192.168.2.5) 56(84) bytes of data.
64 bytes from 192.168.2.5 icmp_seq=1 ttl=62 time=0.239 ms
64 bytes from 192.168.2.5 icmp_seq=2 ttl=62 time=0.296 ms
64 bytes from 192.168.2.5 icmp_seq=3 ttl=62 time=0.268 ms
64 bytes from 192.168.2.5 icmp_seq=4 ttl=62 time=0.369 ms
--- 192.168.2.5 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2019ms
rtt min/avg/max/mdev = 0.352/0.437/0.503/0.063 ms
root@lanhost1:~#
Step 2: Configure the VPN route
The LAN host(s) must know where to route return traffic. Hence, we will add a route for the ionos-cloud-txl LAN subnet (192.168.1.0/24) via the user-on-prem-lhr user-managed gateway's LAN address (192.168.2.5).
ip route add 192.168.1.0/24 via 192.168.2.5
Repeat this process for all on-premises LAN hosts that need to send or receive traffic over the tunnel. At this point, the two sites must establish complete connectivity via the VPN Gateway.
Verify connectivity
You should now be able to ping hosts in the simulated on-premises setup in user-on-prem-lhr from cloud hosts in ionos-cloud-txl and vice-versa.
root@lanhost1:~# -c 5 192.168.2.5
PING 192.168.2.5 (192.168.2.5) 56(84) bytes of data.
64 bytes from 192.168.2.5 icmp_seq=1 ttl=62 time=18.8 ms
64 bytes from 192.168.2.5 icmp_seq=2 ttl=62 time=19.3 ms
64 bytes from 192.168.2.5 icmp_seq=3 ttl=62 time=19.0 ms
64 bytes from 192.168.2.5 icmp_seq=4 ttl=62 time=18.8 ms
64 bytes from 192.168.2.5 icmp_seq=5 ttl=62 time=19.1 ms
--- 192.168.2.5 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4005ms
rtt min/avg/max/mdev = 18.782/18.995/19.270/0.188 ms
root@lanhost1:~#
root@users-vpn-gw:~# -c 5 192.168.1.5
PING 192.168.1.5 (192.168.1.5) 56(84) bytes of data.
64 bytes from 192.168.1.5 icmp_seq=1 ttl=62 time=18.8 ms
64 bytes from 192.168.1.5 icmp_seq=2 ttl=62 time=19.3 ms
64 bytes from 192.168.1.5 icmp_seq=3 ttl=62 time=19.0 ms
64 bytes from 192.168.1.5 icmp_seq=4 ttl=62 time=18.8 ms
64 bytes from 192.168.1.5 icmp_seq=5 ttl=62 time=19.1 ms
--- 192.168.1.5 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4006ms
rtt min/avg/max/mdev = 18.999/19.594/21.062/0.751 ms
root@users-vpn-gw:~#
Summary
You have successfully configured a site-to-site VPN between the IONOS Cloud (ionos-cloud-txl) and a user-managed on-premises setup (user-on-prem-lhr) by utilizing a managed VPN Gateway in the cloud and a user-managed on-premises gateway.
Note: Ensure you remove the VPN Gateway before attempting to delete VMs, LANs, or the VDC.
