How to scan VPN with Nmap

I have Zenmap installed on my Windows machine. How can I scan my VPN network? The command I use is:

nmap -T4 -A -v 192.168.0.1-255

But It is quitting with error:

WARNING: Using raw sockets because ppp0 is not an ethernet device. This probably won't work on Windows.

pcap_open_live(ppp0, 100, 0, 2) FAILED. Reported error: Error opening adapter: The system cannot find the device specified. (20).  Will wait 5 seconds then retry.

pcap_open_live(ppp0, 100, 0, 2) FAILED. Reported error: Error opening adapter: The system cannot find the device specified. (20).  Will wait 25 seconds then retry.

Call to pcap_open_live(ppp0, 100, 0, 2) failed three times. Reported error: Error opening adapter: The system cannot find the device specified. (20)

QUITTING!

you must add -e eth0

Have you installed WinPcap?

You may need this on Windows as the OS does not natively handle raw sockets.