How to add persistent route for 2 VPN connections when interface # varies?

I need to configure split tunnelling with persistent routes for 2 VPN connections on the same computer as the user needs to connect to 2 different corporate servers at the same time. I have a problem though as the VPN interface # varies in some instances and thus the routes are not being used properly and consistently when the VPN connections are established.

Here are the routes I added:

route add -p 192.168.10.0 mask 255.255.255.0 0.0.0.0 IF 24
route add -p 10.8.18.0 mask 255.255.255.0 0.0.0.0 IF 23

24 being the VPN interface number for VPN 1, 23 for VPN 2. See below.

C:\Windows\system32>route print
===========================================================================
Interface List
 24...........................VPN 1
 23...........................VPN 2
 17...da d1 cb e2 2c ad ......Apple Mobile Device Ethernet
  1...........................Software Loopback Interface 1
 12...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter
 13...00 00 00 00 00 00 00 e0 Teredo Tunneling Pseudo-Interface
 14...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #2
 16...00 00 00 00 00 00 00 e0 Microsoft ISATAP Adapter #3
===========================================================================

If I add the routes after connecting to the VPNs then it all works fine but if I disconnect the two VPN connections and then reconnect them in a different order, then the routes are messed up and obviously I can't access the remote networks.

Is there any another way to make the route use a specific interface persistently?

Solution 1:

When multiple VPNs connect in random order, their interface IDs change. Therefor the normal ROUTE -P ADD 10.0.0.0 MASK 255.255.0.0 10.0.0.1 IF 42 does not work. The next time the VPN connects it might have a different interface number.

Powershell has a cmdlet available that adds routes on VPN connection and removes them again when the VPN is disconnected: Add-VpnConnectionRoute. It works without having to specify the interface ID.

The basic syntax is like this:

Add-VpnConnectionRoute -ConnectionName "VPN Connection Name" -DestinationPrefix 10.0.0.0/16

After entering this command, the routes will be created/removed automatically on connection/disconnection of the VPN.