Checking if VPN is working correctly

Question

How to make sure, that all traffic (e.g. from web browser) is passing through VPN and no data is leaking through normal internet interface? Or how to check, what interface (VPN or other) is used by application? Is there any monitoring system tools, that could ensure me whether VPN is working correctly? I'm using OpenVPN client on Windows and Linux.

Answer 1

Basically if split tunneling is turned off, all traffic must flow over the vpn however try tracert command on both Windows and Linux and you should hopefully get a trace of the route that packets take to reach the destination then You'll be able to tell if it's passing through your VPN gateway.

e.g. tracert www.yahoo.com

You can also use an IP address instead of a DNS name.

Answer 2

First of all check your default gateway settings with route or ip route show command. If you want all ip packets from all applications use VPN tunnel your default gateway must be on the VPN server side (for most cases it's the VPN server's IP address). If your default gateway is the same before and after connecting to the VPN then you need to change it manually.

If you have white IP address from your ISP on one of your network interfaces and you have a routing rule to your ISP network with network mask other then /32 then all your traffic for this particular network will pass through your network interface with a white address because connected routes has higher priority.