Hello Tom, thank you for your reply. Yes, these VMs are all running on FreeBSD. I will try to test it with a Debian machine within the next days. While I am pretty sure MTU is not the (only) root cause of this problem, setting it to 1492 bytes on the VMs (interface setting was 1500 bytes) causes a slight improvement to ~ 1.1 MB/sec, which is still way too low. Disabling remote packet filters did not change anything, both VMs and IPFire machine have AES-NI available, thus being able to encrypt a much bigger volume per second (~ 2.1 Gbit/sec on VMs, ~ 267 Mbit/sec on IPFire host). Changing the OpenVPN tunnel MTU to lower values (tested with 1350 and 1300 bytes) did not change anything. Thanks, and best regards, Peter Müller > Peter, > > Is the issue reproducible on different OS and different OpenVPN clients? There’s a chance that the issue lies with FreeBSD or how you are configuring the VMs at different locations. > > Tom > >> On Sep 24, 2019, at 9:23 AM, wrote: >> >> Hello list, >> >> as mentioned several times before, I am experiencing OpenVPN performance >> problems. Since I am out of ideas by now, asking here to help seemed to >> make sense to me, as I am not sure whether it can be traced to a bug or not. >> >> Test setup is as follows: >> (a) IPFire is freshly installed on a testing machine with Core Update 135 (x86_64). >> The machine is connected to the internet via DSL (link has 100 Mbit/sec >> down capacity with MTU set to 1492) and runs dial-in by itself. No >> cascading router or NAT in place here. >> (b) The remote part is a VM hosted at a big German hosting company, with >> FreeBSD 12 installed (OpenVPN 2.4.7). Uplink is 1 Gbit/sec with MTU = >> 1492. >> (c) Both systems are able to submit ICMP packets up to 1492 bits, so MTU >> is set correctly on both interfaces. >> (d) The VM is establishing an OpenVPN roadwarrior connection to the IPFire >> machine, which can be set up successfully and uses AES-256-GCM (SHA 512) >> for data channel. Tunnel MTU is set to 1400 bytes. >> >> Downloading a test file via SCP from the VM using the OpenVPN connection >> takes ages and results in throughput between 400 and 700 kB/sec. While >> normal ICMP latency through the tunnel is around 35 ms, it fluctuates between >> 40 and 500 ms while download is running. >> >> Needless to say, a bandwidth of 700 kB/sec is unacceptable. Disabling >> Suricata speeds up to ~ 1.2 MB/sec, disabling Quality of Service (QoS) >> does not have any big effects. >> >> Since there are some clients using OpenVPN in restricted environments, >> TCP and port 443 is more or less fixed. Switching to UDP causes a small >> improvement (~ 800 kB/sec), but does not seem to cure the root cause. >> >> This effect is reproducible with multiple VMs at multiple locations, >> so I do not think it is related to network outages at one certain hoster. >> >> What am I doing wrong? Is anyone experiencing the same problem? >> >> As mentioned in the Subject line, any help is appreciated. >> >> Thanks, and best regards, >> Peter Müller