Hello OpenVPN community, I've been struggling with this for the past days and I have not made any progress so far. The configuration of OpenVPN was delightfully straight forward and pretty much everything worked out of the box. The only thing wrong with the installation are the transfer speeds. Without OpenVPN "iperf" reports about 300 mbps download speed. As soon as OpenVPN is involved the speed drops to anywhere between 10 and 70 mbps depending on different mtu/crypto configurations. I've been able to reproduce the issue in a simple adhoc VPN. Server (Debian 8): [code]openvpn --dev tun --proto udp --port 11000 --secret static.key --ifconfig 192.168.222.11 192.168.222.10 iperf -c 192.168.222.10[/code] Client (Ubuntu 16.04): [code]openvpn --dev tun --proto udp --port 11000 --secret static.key --ifconfig 192.168.222.10 192.168.222.11 --remote server.ip iperf -s[/code] This gives me about 35 mbps on a link that should be 300 mbps. The situation is much worse when using tcp at 2-11 mbps. I've experimented with countless combinations of tun-mtu/fragment/mssfix/sndbuf/rcvbuf and many more, the maximum I've ever reached was about 60-70 mbps by adding the following parameters: [code]--txqueuelen 15000 --tcp-queue-limit 128 --cipher aes-256-cbc[/code] CPU usage on the client is

This may be of some help: [url]https://community.openvpn.net/openvpn/wiki/Gigabit_Networks_Linux[/url]

Thank you for your reply. That Wiki entry has helped me run this one-line VPN setup for testing as well as the "--cipher aes-256-cbc" parameter which gave some improvement but the speed remains 70mbps or lower. Changes to mtu values generally made the speed worse, no matter the value. Even with encryption completely disabled (--cipher none --auth none) the speed remains below 70 mbps (and below 11 mbps using tcp). Outside of the VPN the connection to the same box is still at 300 mbps.

Maybe as a general question, can this behavior be reproduced by anyone? I.e. using the commands mentioned, can you get almost full link speed? Searching for a cause for normal behavior would be rather pointless :D

If you can describe your network in more detail maybe a bottle neck can be identified. Personally, I get exactly what I pay for out of my internet while using openvpn.

In addition to ^^^^ CPU? CPU supports AES-NI?

Thank you for your replies. It's a Linux workstation on a gigabit network behind an ASUS RT-AC68U router that connects to a remote server (ping 17-20 ms, 1 gbps bandwidth) through cable internet (400/40 mbps). Both CPUs support AES-NI, Server: Intel(R) Xeon(R) CPU E3-1246 v3 @ 3.50GHz Client: Intel(R) Core(TM) i5-6260U CPU @ 1.80GHz Even though my upload is vastly slower than the download I get better upload speed: Download I get about 33 mbps (355 mbps without VPN), upload 38 mbps (41 mbps without VPN). The next test is going to be hooking up the workstation directly to the cable modem, I'll post an update if this makes a difference :) /Edit: Download is about 36 mbps without the router, so minimal difference.

Another interesting test, using the "shaper" option on the server, when it's set to 5000000 (40 mbps) the speed stays the same (36 mbps, same for any shaper value above that). When set to 2500000 (20 mbps) the speed still stays the same, so I get 36 mbps with a 20 mbps limit (and OpenVPN says "Output Traffic Shaping initialized at 2500000 bytes per second"). Reducing shaper to 1250000 (10 mbps) finally limits the bandwidth and I get 10 mbps. Version information, Server: OpenVPN 2.3.4 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Nov 12 2015 library versions: OpenSSL 1.0.1t 3 May 2016, LZO 2.08 Client: OpenVPN 2.3.10 x86_64-pc-linux-gnu [SSL (OpenSSL)] [LZO] [EPOLL] [PKCS11] [MH] [IPv6] built on Feb 2 2016 library versions: OpenSSL 1.0.2g 1 Mar 2016, LZO 2.08

Max upload speed of the server would be 1 gbps, 200 mbps guaranteed.

Try this on your server and then client: [url]https://sourceforge.net/speedtest/[/url]

Very slow transfer speeds

kolargol

was this issue ever resolved. I have same issues with OpenVPN 2.4.1

dancos

No, we haven't been able to solve this and had to abandon OpenVPN unfortunately. We've tried every transfer speed improvement suggestion out there and experimented with a myriad of different configurations but never came close to the line speeds.

300000

you can try adding this on your server config to see if the speed can max or not
sndbuf 3399999
rcvbuf 3399999
push "sndbuf 3399999 "
push "rcvbuf 3399999 "

my server run over 6 months without restart and client can connect at full speed up and down and i am happy , hope it can help your speed trouble.

ejanszen

The answer is easy: You cannot connect with a higher speed than your lowest upload speed.

For instance, if you have like me on the server side a download speed of 75Mb and an upload speed of 8Mb and on the client side a download speed of 30Mb with an upload speed of 4Mb. It is only then logical that the max speed of the VPN connect is 4Mb.

In this example the speed of the VPN connection can only be increased by increasing the upload speed on the client side.

[deleted]

I have the same miserable problem. My upload at home is 12mBit, download at work is at least 50mBit, and yet, I get speeds way below 1mBit.

However, the problem seems to exist when I transfer more smaller files. If I attempt to transfer single bigger file back and forth, seems to work quite well.

We use Sophos Firewall, I will question there, but I see I am not the only one with the problem... any ideas what/how to troubleshoot?

sinister

ejanszen wrote The answer is easy: You cannot connect with a higher speed than your lowest upload speed.

For instance, if you have like me on the server side a download speed of 75Mb and an upload speed of 8Mb and on the client side a download speed of 30Mb with an upload speed of 4Mb. It is only then logical that the max speed of the VPN connect is 4Mb.

In this example the speed of the VPN connection can only be increased by increasing the upload speed on the client side.

So what if like in my case you have identical networks 200 down 10 up on both sides but when transferring a file you max out at 1MB ?

hdagelic

300000 wrote you can try adding this on your server config to see if the speed can max or not
sndbuf 3399999
rcvbuf 3399999
push "sndbuf 3399999 "
push "rcvbuf 3399999 "

my server run over 6 months without restart and client can connect at full speed up and down and i am happy , hope it can help your speed trouble.

😃
Confirm that! I got a 2x speed increase over WiFi. Thanks!!

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