How can I configure SSL VPN/NetExtender for clients with overlapping subnet?
03/26/2020 377 44347
SSL VPN or NetExtender enables us to access the corporate SonicWall LAN subnets over the Internet with secure VPN tunnel. Sometimes the SonicWall LAN subnet and the client's IP on which the NetExtender is installed overlap and in such scenario accessing SonicWall LAN resources is not possible.
This article explains one of the ways to get over this problem. The solution includes configuring a virtual or dummy subnet with same subnet mask as that of SonicWall LAN subnet, which would do one to one mapping (NATing) of virtual IP addresses to the SonicWall LAN IP address.
EXAMPLE: Let's consider the following IP scheme for the purpose of article.
SonicWall LAN subnet 192.168.1.0 mask 255.255.255.0.
LAN subnet of the computer where NetExtender/Mobile connect is installed 192.168.1.0 mask 255.255.255.0.
SSLVPN IP Pool used for NetExtender virtual adapter 10.1.1.0 mask 255.255.255.0
Virtual or dummy subnet used to send traffic on 10.10.10.0 mask 255.255.255.0
This Nat policy allows the translation of the virtual/dummy network to the actual SonicWall LAN network.
Creating an Access rule.
Navigate to Manage | Policies | Rules | Access Rules.
Go to SSLVPN to LAN page and create the following access rule.
Source: SSLVPN IP Pool
Destination: Virtual LAN Subnet
Action : Allow
How to test
When the NetExtender/ Mobile Connect users with overlapping network will try to access the SonicWall LAN they must use an IP address from the virtual/dummy IP subnet. For example Client computer with NetExtender IP- 10.1.1.1 trying to access a server using virtual IP 10.10.10.65. This traffic when reaches SonicWall device it translates the destination IP from 10.10.10.65 to 192.168.1.65(actual LAN IP) and access rule allows traffic from SSLVPN to LAN zone.