Strange, download speed faster when using VPN client + router VPN

[hursey013]

My router (RT-AC68U, 384.3) is configured to tunnel all traffic through an OpenVPN server running on an external VPS. Everything works as expected, my download speeds are slightly slower than when I connect directly to my ISP, but that's to be expected due to the overhead of OpenVPN.

What I can't figure out is if I have a device (phone, laptop) connected to my network, and then use the OpenVPN client on the device to connect to the same external OpenVPN server, the download speeds go up significantly. How can that be if everything is already being tunneled by the router? I only discovered this by accident, and I'm sure there is a reasonable explanation, but I'm having trouble understanding. Any ideas?

 

[ColinTaylor]

my download speeds are slightly slower than when I connect directly to my ISP

the download speeds go up significantly.

So you're saying that your mobile's download speed is now exceeding your ISP's maximum line speed?

 

[hursey013]

So you're saying that your mobile's download speed is now exceeding your ISP's maximum line speed?

No... sorry if that was unclear. Perhaps some numbers would help.

Direct to ISP, ~28Mbps. With VPN running on router, ~18Mbps. Device connected with local VPN client, running though VPN connected router, ~25Mbps.

 

[ColinTaylor]

Hmmm... Sounds like the mobile isn't going via the VPN. Can you check what external IP the phone is using (http://www.whatsmyip.org/), your router's or the VPN server's.

 

[hursey013]

Hmmm... Sounds like the mobile isn't going via the VPN. Can you check what external IP the phone is using (http://www.whatsmyip.org/), your router's or the VPN server's.

Yeah that was my same thought as well but my external IP still shows as my VPN's address, checked it multiple times.

 

[ColinTaylor]

Puzzling. Perhaps you're looking at it the wrong way around. Maybe ~25Mbps is the speed all your clients should be getting. Maybe you should investigate why some clients are only getting ~18Mbps.

For your normally connected devices, is there a difference in speed between wired and wireless? Do you have QoS enabled, if so try turning it off?

 

[RussellInCincinnati]

Puzzling. Perhaps you're looking at it the wrong way around. Maybe ~25Mbps is the speed all your clients should be getting. Maybe you should investigate why some clients are only getting ~18Mbps.

For your normally connected devices, is there a difference in speed between wired and wireless? Do you have QoS enabled, if so try turning it off?

Doubt that a stock version 1 RT-AC68u can do much more than 18 megabits per second with OpenVPN. 18 is about tops.

 

[RMerlin]

Doubt that a stock version 1 RT-AC68u can do much more than 18 megabits per second with OpenVPN. 18 is about tops.

Depends on cipher. I was able to hit 50 Mbps with AES-128-CBC on the RT-AC56U (same CPU).

 

[hursey013]

I know this is probably not how OpenVPN works, but could it be that since the client on the device is using its hardware for some of the encryption overhead, when it passes the already encrypted data through the router's VPN client it has less work to do...?

 

[RussellInCincinnati]

Depends on cipher. I was able to hit 50 Mbps with AES-128-CBC on the RT-AC56U (same CPU).

Thanks, RMerlin. Will investigate how to change to that probably-faster cipher/encryption method with my NordVPN service. Guess it will involve staring at the little client .ovpn config files they download to you. Great idea.

 

[RMerlin]

Thanks, RMerlin. Will investigate how to change to that probably-faster cipher/encryption method with my NordVPN service. Guess it will involve staring at the little client .ovpn config files they download to you. Great idea.

It will depend on whether they offer servers running with AES-128-CBC. Not every provider do, some only support AES-256-CBC.