How to configure Firewall to route all traffic from L2TP VPN client to the remote site via MPLS VPN

08/23/2021 13 20503

DESCRIPTION:

RESOLUTION:

Resolution for SonicOS 6.5

This release includes significant user interface changes and many new features that are different from the SonicOS 6.2 and earlier firmware. The below resolution is for customers using SonicOS 6.5 firmware.

In the below scenario, outside laptop connects to Site A through L2TP VPN. Both Site A and Site B can access to Internet via WAN interface X1, while  there is an MPLS VPN tunnel between these two sites. This article will describe how to route all traffic from terminal laptop to the remote Site B through MPLS VPN tunnel.
 

 
Step 1: Configure L2TP Server on the firewall of Site A.
  Please refer to the KB 5378: Configuring L2TP Server on SonicOS Enhanced

• Navigate to Manage | Users | LocalUsers & Groups,  Click the Edit button of L2TP VPN user (If non existant please create a user)
  

• Add group Trusted Users (Configured for L2TP) in the Groups tab.
  

• Add WAN RemoteAccess Networks in the VPN Access tab.

• Navigate to Manage | VPN | Base Settings page 
• Enable WAN Group VPN | Click the Edit button of  WAN GroupVPN
  
• Select This Gateway Only for option Allow Connections to: at Client tab | Tick options Set Default Route as this Gateway and also Apply VPN Access Control List.

 
 

• Add a routing policy on the firewall of Site A. Go to Manage| Network | Routing | Routing Policies | Click button Add.
• Source: L2TP IP Pool
• Destination: Any
• Service: Any
• Gateway: To SiteB Gateway
• Interface: Select interface connected to MPLS Tunnel
• Metric: 1

 

• On site A, add a NAT policy to translate L2TP IP Pool addresses to the IP address visible on Site B (you can choose IP address of the interface connecting to MPLS tunnel ).
• Navigate to Manage | Rules | NAT Policies | Click button Add.

 

 

Note: when browse NAT policies you will find there is a default NAT policy for  L2TP IP Pool which was generated by system when configuring WAN GroupVPN.  In order to ensure the policy you just created can be hit as default, y ou are required to change the Priority of the NAT policy you just added to be prior to the default NAT Policy by clicking Priority button. In this case,  the priority for the policy is configured as 3.

 

• On the mobile laptop, connect to the L2TP server of site A and ping any LAN subnet IP address of site B or Interet site.
  

• You can capture the packets on Site B to check whether the traffic has been routed.

Resolution for SonicOS 6.2 and Below

The below resolution is for customers using SonicOS 6.2 and earlier firmware. For firewalls that are generation 6 and newer we suggest to upgrade to the latest general release of SonicOS 6.5 firmware.

In the below scenario, outside laptop connects to Site A through L2TP VPN. Both Site A and Site B can access to Internet via WAN interface X1, while  there is an MPLS VPN tunnel between these two sites. This article will describe how to route all traffic from terminal laptop to the remote Site B through MPLS VPN tunnel.
 

How to configure:

Step 1: Configure L2TP Server on the firewall (TZ205) of Site A.
  Please refer to the KB 5378: Configuring L2TP Server on SonicOS Enhanced
 

• Navigate to Users | LocalUsers | Click the Edit button of L2TP VPN user | Add group Trusted Users (Configured for L2TP) in the Groups tab | Add WAN RemoteAccess Networks in the VPN Access tab.

• Navigate to VPN | Settings page | Enable WAN Group VPN | Click the Edit button of  WAN GroupVPN | Select This Gateway Only for option Allow Connections to: at Client tab | Tick options Set Default Route as this Gateway and also Apply VPN Access Control List.
  

 

• Add a routing policy on the firewall of Site A. Go to Network | Routing | Click button Add.

• On site A, add a NAT policy to translate L2TP IP Pool addresses to the IP address visible on Site B (you can choose IP address of the interface connecting to MPLS tunnel ). Navigate to Network | NAT Policies | Click button Add.

Note: when browse NAT policies you will find there is a default NAT policy for  L2TP IP Pool which was generated by system when configuring WAN GroupVPN.  In order to ensure the policy you just created can be hit as default, y ou are required to change the Priority of the NAT policy you just added to be prior to the default NAT Policy by clicking Priority button. In this case,  the priority for the policy is configured as 3.


 

• On the mobile laptop, connect to the L2TP server of site A and ping any LAN subnet IP address of site B or Interet site.
  

• You can capture the packets on Site B to check whether the traffic has been routed.