Bandwidth seems capped

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muzicman0
OpenVpn Newbie
Posts: 4
Joined: Sun Aug 22, 2021 3:32 pm

Bandwidth seems capped

Post by muzicman0 » Mon Dec 13, 2021 6:01 pm

Running OpenVPN Access Server on Ubuntu 20.04 Server Edition (fully updated), and have 200/200 Mbps internet access, but I can't get more than about 80-90 Mbps speed across the VPN. Is there a way to increase this? Would love to get closer to 170-175 Mbps.

Not sure what info might be needed, but I'm happy to provide more info if/when needed.

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openvpn_inc
OpenVPN Inc.
Posts: 1333
Joined: Tue Feb 16, 2021 10:41 am

Re: Bandwidth seems capped

Post by openvpn_inc » Mon Dec 13, 2021 6:22 pm

Hello muzicman0,

There are a multitude of possible reasons for this. There's no silver bullet for this. You'll just have to investigate and try to find out which particular problem is throttling the speed. Here are some tips;

- VPS and cloud providers tend to cap CPU utilization. Investigate this. Verify this.
- Run iperf3 tests between client and server over UDP on same port as OpenVPN traffic (usually 1194 UDP).
- Run OpenSSL encryption speed tests for a longer period (couple of minutes) to see if encryption/decryption is the problem.
- Check buffer settings for TCP and UDP. Traffic may be getting a little stuck here.
- Verify that the OpenVPN connection is using UDP. This is the recommended protocol.
- Note that TCP traffic is likely travelling inside the OpenVPN UDP tunnel and there could be a problem with speed here.
- Try transferring data that exists on the VPN server itself, like copy a file or such using SCP over the VPN tunnel. Compare to trying to get information from an external system. There could be bottleneck elsewhere in the network.
- Keep in mind data that is transferred through the VPN tunnel has to exit/enter the VPN server too. So if you redirect VPN client's internet traffic through the VPN server, keep in mind that downloading a file through there means the server is downloading AND uploading that file. The internet connection of the server may only be able to do one of these well. Or it could drop the speed to accomodate both streams of traffic.

As I've said, there's no single silver bullet that will do the trick. However we don't usually need to do anything 'special' to make it work well. In your case you may be running into some limit somewhere, problem is figuring out which one. I'm afraid I can't help much more than that.

Good luck,
Johan
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