VPN L2TP
Windows Server: Eth1: NAT Eth2: Custom (192.168.10.1/24)
Windows 10: Eth1:Custom (192.168.10.100/24 , GW: 192.168.10.1)
Step 1: Configure Routing and Remote Access
Open Server Manager and Add Roles and Feature> Add Remote Access “RAS and Routing”
Step 2: Configure Routing and Remote Access
On the left pane, right-click on your local server and click Configure and Enable Routing and Remote Access.
In Configure and Enable Routing and Remote Access Wizard, select Custom Configuration radio button as we will manually configure the routing and access. Click Next button.
Next, select VPN Access and NAT checkboxes and click next to see a summary of the selection.
Finally, on clicking Finish button, you will see a prompt to start the Routing and Remote Access Services. Click on the Start Service button.
Step 3: Configure VPN Properties
Now that we have our VPN running, let’s go ahead and configure it. Under the Routing and Remote Access window, on the left pane, right-click on your local server and click Properties.
Navigate to the security tab and click on Allow custom IPSec policy for L2TP/IKEv2 connection and put a very long PSK(Pre-shared key). You can use any tool to generate a random key.
Make sure to note down the PSK as we will need to share the PSK with every user who wants to connect to the VPN server.
Now, go to IPv4 tab and under IPv4 address assignment select static address pool. Click Add button and you will get a pop up to put IP address ranges. Put the starting address and ending address of the IP address range you want the users to assign to.
Click the OK button to save the address range and finally click OK to save the changes. You may get a warning saying you need to restart the Routing and Remote Access for changes to apply, you can safely click OK and ignore it for now as we will restart the service after completing the next step. Take a screenshot of your range of IP addresses.
Step 4: Configure NAT
On the same left pane of Routing and Remote Access window, expand your local server and then expand IPv4. You will see the NAT object there. Right-click on NAT and then click on New Interface option.
Select Ethernet and click OK to proceed further. On the NAT tab, select Public interface connected to Internet radio button and also select Enable NAT on this interface checkbox.
Now, go to Services and Ports tab and select VPN Server(L2TP/IPSec – running on this server) checkbox. It will open up a new interface for editing the service. Take a screenshot
Change the private address from 0.0.0.0 to 127.0.0.1 and click OK to save.
Finally, Click OK to save the NAT interface.
Step 5: Restart Routing and Remote Access
On the left pane of the Routing and Remote Access window, right-click on your local server and click on Restart under All Tasks.
This will restart the Routing and Remote Access services and all the changes we have made will be applied.
Step 6: Configure Windows Firewall
On the start menu, search for Windows defender firewall and open it. Click on Advanced settings on the windows defender firewall.
Under Advanced setting, click on Inbound Rules on the left pane and then click on New Rule on right side pane.
Windows Server 2019 has predefined rules which we need to enable for VPN to work. In New Inbound Rule Wizard click on Predefined radio button and select the Routing and Remote Access from the drop-down.
Under Predefined Rules select Routing and Remote Access(L2TP-In) checkbox and click Next.
Under Action select, the option Allow the connection and click Finish.
The firewall is now configured to allow inbound traffic on UDP port 1701.
Step 7: Create VPN User
Search for Computer Management in the start menu and under Computer Management window expand Local users and group.
Right-click on Users and click on New User under Local users and group to create a new user.
On New User prompt, provide a username, full name, and strong password. Uncheck User must change the password on next login checkbox. Click Create to create a new user. Take a screenshot
Once the user is created, return to the Computer Management interface and you will find the user which you have just created in the list of users. Right-click on the user and click the Properties option.
On your VPN users properties, navigate to Dial-in tab. Now, select Allow access option for Network Access Permissions setting. Click OK to save the properties. Take a screenshot
Our L2TP/IPSec VPN server is now ready and can accept the connections.
Step 8: Connecting VPN Client
You will need to share the PSK and Windows username and password to the user who wishes to connect to the remote VPN server. Create a VPN connection L2TP on windows and enter the key under the security tab for your connection.
Step 9: Monitoring VPN
Search for Remote Access Management Console in the start menu and open the console. You should see the status of the VPN. If you have followed the tutorial correctly, you will see all green checkmark on all services. You can also view the details of connected clients on this console.
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