Configuring L2TP Server on SonicOS Enhanced
03/26/2020 
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DESCRIPTION:
This document explains how to configure L2TP Client access to the SonicWall WAN GroupVPN SA using the built-in L2TP Server and Microsoft's L2TP VPN Client.The suggested configuration was confirmed to work with Microsoft Windows XP Service Pack 2 (SP2), Vista Ultimate, and Vista Home .
RESOLUTION:
- Click MANAGE , navigate to VPN | Base Settings and enable the WAN GroupVPN policy. The default policy settings are OK to use, but the Shared Secret will be needed for the client policy configuration.
- Enable the Accept Multiple Proposals for Clients checkbox which allows multiple VPN or L2TP clients using different security policies to connect.
I. Enable the L2TP Server. Click 'Configure'
II. L2TP Server Settings
Keep alive time (secs): 60
DNS Server 1: (Use internal or your ISP's DNS)
DNS Server 2: 4.2.2.2 (or use your ISP's DNS)
DNS Server 3: 0.0.0.0 (or use your ISP's DNS)
WINS Server 1: 0.0.0.0 (or use your WINS IP)
WINS Server 2: 0.0.0.0 (or use your WINS IP)
III. IP Address Settings
IP address provided by RADIUS/LDAP Server: Disabled
Use the Local L2TP IP Pool: Enabled
Start IP: 10.20.0.1 *EXAMPLE*
End IP: 10.20.0.20 *EXAMPLE*
IV. L2TP Users
User Group for L2TP Users: 'Trusted Users' |
- Navigate to Rules| NAT Policies. SonicOS Enhanced will automatically add the following NAT policy.
- Navigate to Rules| Access Rules and select VPN to WAN and Add the following rule.
L2TP setup on the Client computer
This next steps are performed on a workstation running Microsoft Windows XP Professional, Service Pack 2.
- Go to the Control Panel.
- Navigate to Network Connections.
- Open the New Connection Wizard. Click Next.
- Choose Connect to the network at my workplace.Click Next.
- Choose Virtual Private Network Connection. Click Next.
- Enter a name for your VPN connection. Click Next.
- Enter the Public (WAN) IP address of the SNWL. Alternatively, you can use a domain name that points to the SNWL. Click Next, then click Finish. The connection window will appear. Click Properties.
- Go to the Security tab. Click on IPSec Settings. Enable Use pre-shared key for authentication. Enter your pre-shared secret. Click OK.
- Navigate to the Networking tab. Change type of VPN from Automatic to L2TP IPSec VPN. Click OK.
- Enter your XAUTH username and password. Click Connect.
NOTE: Once the connection has been established, Internet access should be available. Access to the internal network will also be available.
Troubleshoot:
If the client does not connect right away consult the client logs and SonicWall logs. In same cases the client will send an SA delete request which is a NAT-T related error. After disabling NAT traversal on both the client and upstream firewall the client should then be able to connect.
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