Create an IPSec Tunnel between two VDCs
Overview
This tutorial demonstrates how users can configure the VPN Gateway product in IONOS CLOUD to create an IPSec based site-to-site setup between two VDCs in different regions.
This tutorial demonstrates the use of the following:
Components
Description
Two VDCs
Provisioned in locations Berlin ionos-cloud-txl and London ionos-cloud-lhr respectively.
Managed gateways
We will use a managed IPSec instance to provide secure, encrypted connectivity between two VDCs in IONOS CLOUD.
Target audience
This tutorial is intended to help both developers and technical decision-makers.
What you will learn
By following this tutorial, you will learn how to:
Provision managed IPSec VPN Gateways in IONOS CLOUD across different regions.
Configure site-to-site IPSec tunnels between two VDCs.
Generate and use secure pre-shared keys for authentication.
Set up LAN subnets and assign gateway addresses.
Configure tunnel parameters including encryption, integrity, and network CIDRs.
Manually add routing rules to enable traffic between VDCs.
Verify secure connectivity between hosts in separate VDCs.
Before you begin
The following information is necessary to set up an IPSec connection between two VDCs:
Components
Berlin VPN ionos-cloud-txl
London VPN ionos-cloud-lhr
VDC Name
ionos-cloud-txl
ionos-cloud-lhr
Gateway Public Address
203.0.113.10
203.0.113.20
LAN ID
1
2
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.
Reserve your IPs
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.
Components
Berlin VPN ionos-cloud-txl
London VPN ionos-cloud-lhr
Gateway Public Address
203.0.113.10
203.0.113.20
Configure LAN
This tutorial uses 10.10.1.0/24 and 10.10.2.0/24 for private LANs in the IONOS CLOUD. 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
Berlin VPN ionos-cloud-txl
London VPN ionos-cloud-lhr
LAN ID
1
2
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:
Execute either of these commands:
openssl rand -base64 48
OR
head -c 32 /dev/urandom | base64
Procedure
Setup VDCs
Below are some screenshots from the DCD that contains the required VDCs.
1. VDC in ionos-cloud-txl
To begin with, two virtual servers are provisioned in the location ionos-cloud-txl and connected to each other via a private LAN. In this instance, LAN1 uses a custom subnet 192.168.1.0/24. We designate these two servers as 192.168.1.11 and 192.168.1.12, respectively.
2. VDC in ionos-cloud-lhr
Similar to the ionos-cloud-txl VDC, two virtual servers are provisioned in ionos-cloud-lhr and connected to each other via a private LAN. In this instance, LAN2 uses a custom subnet 192.168.2.0/24. We designate these two servers as 192.168.2.11 and 192.168.2.12, respectively.
Provision the VPN Gateways
This will need to be repeated for both sites, referring to the table of configuration parameters:
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:
Enter the following before proceeding:
Components
Description
Example
Name
A descriptive name for the gateway instance, this does not need to be globally unique. Restricted to 255 characters.
vdc-to-vdc
Location
A list of available locations for VPN Gateway configuration.
ionos-cloud-txl
IP Address
A list of available public IPv4 addresses.
203.0.113.10
Description
More descriptive text for the gateway, limited to 1024 characters.
VPN Gateway for creating an IPSec Tunnel between VDCs.
Note: You can only upgrade the tier or switch between High Availability (HA) and non-HA variants during editing.
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.
The IPSec protocol is selected by default and no other configuration parameters are required.
Attach a VPN Gateway to LANs in IONOS CLOUD. Note that it is only possible to connect to LANs in the exact location where the VPN Gateway was provisioned. Let us look at the parameters required:
Components
Description
Example
Datacenter
Select a data center from the drop-down that lists VDCs in the same location as the gatweway.
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
Define a maintenance window to begin at the specified start time (UTC) and continue for a duration of four hours. Specify the following:
Components
Description
Example
Day
Select a day from the drop-down list to set a day for maintenance.
Sunday
Time
Enter a time using the pre-defined format (hh🇲🇲ss) to schedule the maintenance task.
01:40 AM
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.
Note: Repeat this process for the ionos-cloud-lhr location to create a managed IPSec gateway there too using the parameters table to set the required properties correctly.
Configure the VPN Tunnels
Now that the VPN Gateway instance is provisioned, the next step is to configure a tunnel to permit the two sides to talk with each other. We will need to configure a tunnel on both instances of the managed gateway.
1. Click Create Tunnels to begin configuring a new tunnel.
2. Configure the Tunnels for ionos-cloud-txl and ionos-cloud-lhr, respectively.
a. ionos-cloud-txl Tunnel Configuration
Enter the following details to configure a tunnel:
Components
Description
Example
Tunnel Name
A name for the tunnel, this does not need to be globally unique and is limited to 255 characters.
lhr-tunnel
Description
More descriptive text for the peer, limited to 1024 characters.
Not Applicable
Remote Host
The Gateway Public IPv4 address of the remote VPN Gateway.
203.0.113.20
Set the PSK as shown:
Components
Description
Example
Pre-Shared Key
A strong key, minimum of 32 characters
vPabcdefg123435hij565k7lmno8pq=
This tab displays the Initial Exchange (IKE_SA_INIT) Settings.
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 the purposes of the demonstration, the available options are aligned with BSI best practices. However, we will accept the default selections.
Components
Description
Example
Encryption Algorithm
Encryption algorithms protect the data so it cannot be read by a third-party while in transit.
AES128-CTR
Integrity Algorithm
Integrity algorithms provide authentication of messages and randomness, ensuring that packets are authentic and were not altered by a third party before arriving, and also for constructing keying material for encryption.
SHA256
Diffe-Hellman
The Diffie-Hellman (DH) key exchange algorithm is a method used to make a shared encryption key available to two entities without an exchange of 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
Lifetime
The length of time (in seconds) that a negotiated IKE SA key is effective. 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
This tab displays the Child SA/IPSec SA Settings (ESP) settings.
Note: Both sites typically have the same ESP 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 ESP phase. For the purposes of the 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 an exchange of 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 protect the data so it cannot be read by a third-party while in transit.
AES128-CTR
Integrity Algorithm
Integrity algorithms provide authentication of messages and randomness, ensuring that packets are authentic and were not altered by a third party before arriving, and also for constructing keying material for encryption.
SHA256
Lifetime
The ESP SA determines how long the keys generated during the IKE negotiation are valid for encrypting and authenticating the actual data packets being transmitted.
3600
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.
Configure the subnets in CIDR format, which are permitted to connect to the tunnel.
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 side that are permitted to connect to the tunnel.
192.168.2.0/24
b. ionos-cloud-lhr Tunnel Configuration
Enter the following details to configure a tunnel:
Components
Description
Example
Tunnel Name
A name for the tunnel, this does not need to be globally unique and is limited to 255 characters.
txl-tunnel
Description
More descriptive text for the peer, limited to 1024 characters.
N/A
Remote Host
The Gateway Public IPv4 address of the remote VPN Gateway.
203.0.113.10
3.2 Authentication
This is where the Pre-shared key (PSK) is set.
Components
Description
Example
Pre-Shared Key
A strong key, minimum of 32 characters.
vPabcdefg123435hij565k7lmno8pq=
This tab displays the Initial Exchange (IKE_SA_INIT) Settings.
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 the purposes of the 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 an exchange of 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 protect the data so it cannot be read by a third-party while in transit.
AES128-CTR
Integrity Algorithm
Integrity algorithms provide authentication of messages and randomness, ensuring that packets are authentic and were not altered by a third party before arriving, and also for constructing keying material for encryption.
SHA256
Lifetime
The length of time (in seconds) that a negotiated IKE SA key is effective. 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
This tab displays the Child SA/IPSec SA Settings (ESP) settings.
Note: Both sites typically have the same ESP 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 ESP phase. For the purposes of the demonstration, the available options are aligned with BSI best practices. However, we will accept the default selections.
Components
Description
Example
Diffie-Hellman
The Diffie-Hellman (DH) key exchange algorithm is a method used to make a shared encryption key available to two entities without an exchange of 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 protect the data so it cannot be read by a third party while in transit.
AES128-CTR
Integrity Algorithm
Integrity algorithms provide authentication of messages and randomness, ensuring that packets are authentic and were not altered by a third party before arriving, and also for constructing keying material for encryption.
SHA256
Lifetime
The ESP SA determines how long the keys generated during the IKE negotiation are valid for encrypting and authenticating the actual data packets being transmitted.
3600
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.
Configure the subnets in CIDR format, which are permitted to connect to the tunnel.
Components
Description
Example
Cloud Network CIDRs
Network addresses on the cloud side that are permitted to connect to the tunnel.
192.168.2.0/24
Peer Network CIDRs
Network addresses on the peer side that are permitted to connect to the tunnel.
192.168.1.0/24
3. Click Save to save the tunnel configuration. This operation usually takes about one to two minutes to complete.
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 VDCs.
1. Configure ionos-cloud-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, 192.168.1.5. Begin by pinging the IP address:
Step 2: Configure the VPN route
The LAN host(s) must know where to route the return traffic. To accomplish this, we will add a route for the ionos-cloud-lhr LAN subnet 192.168.2.0/24 via the ionos-cloud-txl gateway's LAN address 192.168.1.5:
We cannot ping hosts in the ionos-cloud-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 ionos-cloud-lhr.
2. Configure ionos-cloud-lhr 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 that does not have an internet access. Open a console session and ping the LAN address assigned to the VPN Gateway, 192.168.2.5. Begin by pinging the IP address:
Step 2: Configure the VPN route
The LAN host(s) must know where to route the return traffic. To accomplish this, we will add a route for the ionos-cloud-txl LAN subnet 192.168.1.0/24 via the ionos-cloud-lhr gateway's LAN address 192.168.2.5:
At this point, full connectivity between the two sites via the VPN Gateway is established.
Conclusion
You have successfully configured a site-to-site IPSec VPN between two IONOS CLOUD VDCs using a Managed VPN Gateway.
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