I'm currently having some issues with connecting the VPN to my Vnet properly.

The Virtual Network is called MGS-vnet with an address space of

It contains 2 subnets:

  1. default with an address range of
  2. GatewaySubnet with an address range of

I then have a Virtual Network Gateway, aptly named VPN.

Under MGS-vnet there is a VM called MGSServ1 which is connected by a network inteface mgsserv1261 and assigned the IP address

The issue is that I can't get the VPN to communicate with the MGSServ1, I've attempted with some different netmasks since I noticed that might've been the issue so I changed the address space to which is now my current configuration, I believe this would be the correct configuration but that address space means I cannot specify an address range on the Point-To-Site that isn't already reserved.

Failed to save virtual network gateway 'VPN'. Error: The virtual network gateway's VPN client address pool overlaps with the virtual network's address space. The overlapping address space prefixes are and

Hope you can advise where the issue is in creating this connection between the VPN and the VM.

I've also attempted with creating a Route Table between the IP range of VPN to the specific VM, I was unable to get that working and not sure if I should proceed with that solution.

Network Diagram

Networking Diagram


The issue is stated in the error message you provided The overlapping address space prefixes are and Your Point-To-Site (P2S) address space cannot be in the VNet Address space. Easy fix change P2S address space to something else like, that should work.

The questions is do you need all host in /8 or /16? because you are bound to running into lots of overlapping issues.

If you really need all the hosts, recommendation:

Configure MSG-VNet to

Default Subnet to --You can add more subnet as needed

GateWay Subnet to --Smallest subnet possible /29

If not, keep it simple, recommendation:

Configure MSG-VNet to

Default Subnet to

GateWay Subnet to --Smallest subnet possible /29

Good Luck.......

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  • I actually figured out that this was a non-issue, if I returned to my previous setup and had the IP addresses seperate, it could still connect. The reasoning behind this was me testing for a shared drive to see if the connection was there, I also tried to ping the IP which was not sufficient, if I connected through RDP to the internal IP address I could access the VM. The issue was then port-blocking issues with port 445 since I could not see the shared drives. – Boringuity Nov 1 '18 at 11:13
  • A port query tool should help you identify port blocking issues. As for 445, SMB port it is blocked by almost all ISPs and work networks.https://support.microsoft.com/en-us/help/3185535/guidelines-for-blocking-specific-firewall-ports-to-prevent-smb-traffic – Hannel Nov 1 '18 at 18:42

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