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Barracuda CloudGen Firewall

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How to Configure the NG SSL VPN Service

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The SSL VPN service is part of the VPN service on the Barracuda NG Firewall. Configure the SSL VPN to listen on a public IP address and to authenticate the users via an external authentication server. It is recommended to use signed SSL certificates to avoid SSL error messages for the users when connecting to the NG SSL VPN. NG SSL VPN is supported for Barracuda NG Firewall F180 and larger, as well as all Barracuda NG Firewall Vx models.

In this article:

Before you Begin

  • A Remote Access basic or premium subscription is required to use the NG SSL VPN.
  • Because the VPN service can also listen on port 443, verify that Use Port 443 is set to No in the Server Settings on the VPN Settings page.  
  • Verify that the IP address you want the SSL VPN to listen on is configured as as Virtual Server and VPN service IP address. For more information, see Virtual Servers and Services
  • Configure an external authentication server or NGF local authentication. For more information, see Authentication

Step 1. Enable the SSL VPN

  1. Go to CONFIGURATION > Configuration Tree > Box > Virtual Servers > your virtual server > Assigned Services > VPN-Service > SSL-VPN.
  2. Click Lock.
  3. Set Enable SSL VPN to Yes.

  4. Click + to add a Listen IP.

  5. (recommended) Enable Restrict to Strong Ciphers Only.


  6. Select the Identification Type
    • Generated-Certificate – The certificate and the private key is automatically created by the Barracuda NG Firewall.
    • Self-Signed-Certificate – Click New to create a Self-Signed Private Key and then Edit to create the Self-Signed Certificate.
    • External-Certificate – Click Ex/Import to import the CA-signed External Certificate and the External-Signed Private Key.
  7. Click Send Changes and Activate.

Step 2. Configure Authentication and Login

Configure the authentication server and the allowed and blocked user groups. Users that are not members of one of these groups will be denied access to the NG SSL VPN.

  1. Go to CONFIGURATION > Configuration Tree > Box > Virtual Servers > your virtual server > Assigned Services > VPN-Service > SSL-VPN.
  2. In the left menu, click Authentication & Login.
  3. Click Lock.
  4. From the Authentication Scheme list, select your authentication method.  
  5. If you are using an authentication service with group information, or an authentication helper scheme to provide group information, set Use Group Policies to yes.
  6. Click + to add Allowed User Groups.
  7. Click + to add Blocked User Groups 
  8. (optional) Configure the following settings as needed:  
    • Use Max Concurrent Users – Enable to limit the number of simultaneous users using the NG SSL VPN.
    • Max Concurrent Users – Enter the maximum number of users that simultaneously can be connected to the NG SSL VPN. 
    • Cookie Timeout (Min) – Enter the session timeout in minutes.
    • Authentication Request Timeout (sec) to a value up to 20 seconds if you are using multi-factor authentication.  
    • Browser Cleanup – Enable to clear the browser cache after logging out. Only for Internet Explorer and Firefox.   
    • Deny Autocomplete – Set to yes to disable auto completion for the HTML forms in the SSL VPN.   
    • Deny Remember Me – Set to yes to remove the Remember me checkbox on the login page.
  9. Customize the login messages and logos:  
    • (optional) Import a Logo.

      It is recommended to use a 200 x 66px PNG or JPG image.

    • (optional) Enter a plain text Login Message. E.g, Welcome to the Barracuda NG SSL VPN.
    • (optional) Enter a HTML Help Text.
  10. Click Send Changes and Activate.

Step 3. (optional) Enforce Strong Ciphers

Replace the default ciphers by a more secure spec.

  1. Go to CONFIGURATION > Configuration Tree > Box > Virtual Servers > your virtual server > Assigned Services > VPN-Service > SSL-VPN.
  2. Click Lock.
  3. In the left menu expand Configuration Mode and click on Switch to Advanced View.
  4. Disable Allow SSLv2 and Allow SSLv3
    Enable Restrict to Strong Ciphers Only

    For Barracuda NG Firewalls versions 6.1 and below, Barracuda Networks strongly recommends to set the following custom SSL Cipher Spec settings to mitigate CVE-2015-4000 aka. Logjam.

  5. Enter the SSL Cipher Spec: RSA:EDH:!EXP:!NULL:+HIGH:-MEDIUM:-LOW:-SSLv2:-IDEA-CBC-SHA
  6. Click Send Changes and Activate.


  • If the sslvpn log contains the following line: http_listener: failed to listen on <IP address>@443 verify that no other service on the Barracuda NG Firewall is running on that port and no DNAT access rules are redirecting the traffic to a different IP address.
  • When updating or changing certificates, the SSL VPN service needs to be restarted:
    1.  Set Enable SSL VPN to no.
    2.  Click Send Changes and Activate.
    3.  Set Enable SSL VPN to yes.
    4.  Click Send Changes and Activate.
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