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Barracuda NextGen Firewall X

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End-Of-Life and End-Of-Support on December 1st, 2020: All Barracuda Firewall X-Series sales will cease; neither new sales nor any renewals will be available. If you currently hold a maintenance and support contract, you will continue to receive our award-winning support and services until your contract expires. Please see the End-Of-Life definition as described in the End of Support and End of Life Information.

How to Configure a Client-to-Site VPN with Certificate Authentication

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Step 1. Enable the VPN service on a network interface

Enable the VPN service on a static IP address. If you do not have a static WAN IP address, you must enable the VPN service for a static internal interface and then redirect incoming connections to the VPN service with a firewall rule.

Static (fixed) WAN IP address

To enable the VPN service for the static network interface:

  1. Go to the NETWORK > IP Configuration page.
  2. In the Static Interface Configuration section click Edit to configure your static WAN interface. 
  3. In the Edit Static Network Interface window, select the VPN Server check box.

    If SSL VPN service is also enabled for this interface, go to the VPN > Site-To-Site VPN page and disable the Use TCP Port 443 setting for the VPN service.

  4. Click Save
Dynamic (DHCP/3G/PPPoE) WAN IP Address

You must have an active DynDNS account, so that the client can connect to the dynamic IP address. For more information on creating a DynDNS account, see

To use the VPN service with a dynamic WAN IP address, run the VPN service on an internal IP address. Do not use the management IP address; instead, add a secondary IP address. Then, create an access rule to redirect all incoming VPN traffic from the dynamic interface to the VPN service.

  1. Go to the NETWORK > IP Configuration page.
  2. Enable dynamic DNS.
    1. In the Dynamic Interface Configuration section, click Edit to configure the dynamic WAN interface. 
    2. In the Edit Dynamic Network Interface window, enable Use Dynamic DNS.
    3. Enter the DynDNS Hostname and authentication information.

    4. Click Save.
  3. In the Management IP Configuration section, enter a secondary IP address: 
    • IP ADDRESS – Enter an IP address that is free in the local network. For example, if the MIP address is in the network.
    • VPN SERVER – Select this check box. 


  4. Click Add.
  5. Create an access rule to redirect incoming VPN connections on the dynamic interface to the VPN server listening on the local IP address.
    1. Go to the FIREWALL > Firewall Rules page.
    2. Click Add Access Rule.
    3. In the Add Access Rule window, configure a Redirect to Service firewall rule.
      • For the Destination, select the network object corresponding to your Internet connection type (DHCP, 3G, or DSL).
      • For the Redirected To setting, select the VPN network object.
    4. Click Save.
  6. Move the access rule above the BLOCKALL rule so it is the first access rule to match incoming VPN traffic. For more information, see Firewall Rules Order.
  7. Click Save.

Step 2. Upload or create certificates

Use a third-party PKI to create the VPN and client certificates. For more information on how to create certificates, see How to Create Certificates with XCA and How to Create Certificates for a Client-to-Site VPN.

The SubAlt name of the VPN server certificate must be DNS: or DNS: *. If you are using an FQDN, it must resolve to the IP address of the X-Series Firewall VPN service.

  1. Go to the ADVANCED > Certificates page.
  2. Click Upload.
    • Certificate Name – Enter VPN Certificate.
    • Certificate Type – Select the type of certificate you want to upload.
    • Add to VPN Certificates – Enable the checkbox.
    • Certificate File – Select the certificate file you want to upload.
  3. Click Save.

Step 3. Configure client-to-site VPN settings

Configure user authentication and IPsec settings.

Step 3.1 Configure user authentication and select the certificate
  1. Go to the VPN > Client-To-Site VPN page. 
  2. In the Settings section, select a User Authentication method. You can use local or external user authentication.
  3. From the Local Certificate list, select the certificate that you created in Step 2 (e.g., VPNCertificate).
  4. Click Save.
Step 3.2 Configure IPsec settings for certificate authentication
  Configure the authentication type and, if needed, the encryption algorithms for IPsec phase 1 and 2.
  1. Go to the VPN > Client-To-Site VPN page.
  2. In the IPsec Settings section select Client Certificate as the Authentication type.
  3. (optional) Configure the IPsec Phase 1 Settings and IPsec Phase 2 Settings.

    Do not change the default IPsec Phase 1 and Phase 2 settings if you want to use iOS or Android devices as VPN clients,

  4. Click Save.
Step 3.3 Create a VPN access policy

Define the VPN clients and network information to be passed to client.

Access policies are matched based on the Allowed Group of the access policy from top to bottom. Make sure access policies are entered so the more specific allowed groups are on the top of the list and the generic * conditions are on the bottom of the list.

  1. Go to the VPN > Client-To-Site VPN page.
  2. In the VPN Access Policies section, click Add Access Policy
  3. In the Add VPN Access Policy window, configure the following settings: 
    • Name – A name for the access policy.

      The name of the access policy is referred to as group name on iOS and Android devices.

    • Client Network – The network that the client will be assigned to (e.g.,

    • (Optional) Domain – The domain assigned to the client.
    • Primary DNS Server – The IP address of the DNS server.
    • Published Networks – The local networks available for the VPN client.

      Add to the Published Networks to allow the client to access the Internet through the VPN tunnel.

    • IPsec Phase 2 – The IPsec Phase 2 settings that you configured in Step 3.2 (e.g., Client2SiteVPNClients from the example in Step 3.2).
    • No Split Tunnel Mode – Enable to lock down the client to only connect to the Published Networks of the VPN tunnel. Windows hosts using the Barracuda VPN client only.

      Enabling this option blocks VPN access for all non-Windows clients!

    • Allowed Peers – Enable IPsec Clients for mobile devices and third-party IPsec clients and Barracuda VPN client to be able to connect with the Barracuda VPN client.
    • Allowed Groups – The groups that are allowed to connect. To allow all groups, enter an asterisk (*).
    • Use for CudaLaunch – Enable self-provisioning on Windows, macOS, or iOS devices for remote clients using the CudaLaunch portal. For more information, see CudaLaunch.
      Configure the following settings:
      • CudaLaunch Server – Enter the IP address of the server providing CudaLaunch.
      • Allowed Groups – Enter the user groups that the policy applies to. Click after each entry. You can use question marks (?) and asterisks (*) as wildcard characters.
  4. Click Save.

Step 4. Configure clients

Configure VPN clients to connect to the IPsec VPN with certificate authentication.

Barracuda VPN clients

Configure the Barracuda VPN client to connect to the IPsec VPN with certificate authentication you just created.

  1. Go to the VPN > Client-To-Site page.
  2. Download and install the Barracuda VPN Client.
    1. In the Settings section, select your operating system from the Download Barracuda VPN Client list and click Download. 
    2. Install the Barracuda VPN Client. You must have administrative rights. 
    3. Reboot the computer after the installation.
  3. Configure a profile for connecting to the IPsec VPN.
    1. Start the Barracuda VPN Client.
    2. In the left pane, click Preferences.
    3. In the Barracuda VPN Control window, right-click the default profile and select Modify Profile. 
    4. In the Properties window, specify these settings:
      • Certificate – Select X509 authentication.
      • Remote Server – Enter the WAN IP address or DynDNS name (e.g., or in the Host names or IP addresses of remote server field.
    5. Click OK
  4. Close the Barracuda VPN Control window.

After configuring the Barracuda VPN client, you can connect to the IPsec VPN:

  1. Start the Barracuda VPN Connector.
  2. Enter your Username and Password.
  3. Click Connect. 

You are now connected to the client-to-site IPsec VPN with the Barracuda VPN Client.


The connection status is displayed on the VPN > Active Connections page.


Mobile clients

For instructions on configuring mobile clients, see these articles:

Mobile OSSupported VersionArticle
Apple iOS5.2 and aboveHow to Configure the Apple iOS VPN Client for IPsec Shared Key VPN
Android4.0 and aboveHow to Configure the Android VPN Client for IPsec Shared Key VPN
Third-party IPsec VPN clients

The X-Series Firewall adheres to the IPsec standard. Any third-party IPsec client implementing this standard can connect to the IPsec VPN.