OpenVPN slow transfer speeds from mapped network drive

I have openvpn running on pfsense, and is connected from alt location. A speedtest from alt location gives me ~250/250mbit on a laptop. A speedtest on the server will give ~900/900mbit. So internet speeds are ok.
When connected to openvpn, start a file transfer from a mapped network drive, speeds are ~11/15mbit. Openvpn is running on a qotom w. i3-4025U, and by looking at cpu usage, there seems to be plenty of headroom.
Could this have anything to do with “force all traffic” through the vpn? I normally have it off, but a test did not seem to change anything.
Secondly, when/if you switch on the “force all traffic” do you need to do anything client side, like reconnect, change a setting or other?


  • TCP or UDP for OpenVPN? TCP can cause slowness

  • Is compression enabled?

  • Is the VPN using heavy encryption? (Blowfish recommended for fastest)

  • Have you checked MTU values? ping -f -l <size> server Start with 1472. If you get fragmenting go up or down by increments of 10 . Add 28 to the largest number that does not fragment and test again.

  • Does the MTU match on both sides?

  • OpenVPN is single threaded. Check to see if you are getting a single core bottleneck.

Hopefully someone else with a better idea will be around.

This might be of help:

I am unsure about this.