OPNsense Forum

English Forums => Virtual private networks => Topic started by: PANZER on October 26, 2025, 12:57:51 PM

Title: OpenVPN bad connection performance
Post by: PANZER on October 26, 2025, 12:57:51 PM
Hello everyone,

I currently have a "server" with the following specifications:

- i7-6700
- 32GB RAM

HyperV runs on the server as a hypervisor with an OPNsense (24.7.12_4) and a Linux VM.

The firewall has the following interfaces:

- WAN (192.168.2.0/24) = actual home network
- LAN (192.168.100.0/24) = network where the Linux VM is located => behind the firewall
- MGMT (10.10.20.0/24) = management network, e.g., to access the GUI from the hypervisor
- OpenVPN (10.99.99.0/28) = tunnel network for OpenVPN

The VPN works fine as long as there are no demanding tasks such as RDP. However, as soon as I want to access the Linux VM via RDP, it starts to lag, i.e., the latency is very high. It is almost impossible to use the VM via RDP. So I checked the quality of the connection and found the graph in the attachment.

I have already checked/adjusted the following steps

- Set up and compared WireGuard
- Tested different MTUs
- Activated MSS fix
- Tested TCP/UDP
- Keep alive interval = 10
- Keep alive timeout = 60
- Checked VM resources => None come close to 50%
- Checked Firewall LiveLog
- Reduced RDP connection itself to 15 bits


A ping to the VM yields the following:
Ping is executed for 192.168.100.42 with 1400 bytes of data:
Reply from 192.168.100.42: Bytes=1400 Time=5ms TTL=63
Reply from 192.168.100.42: Bytes=1400 Time=10ms TTL=63
Reply from 192.168.100.42: Bytes=1400 Time=6ms TTL=63
Reply from 192.168.100.42: Bytes=1400 Time=4ms TTL=63

Ping statistics for 192.168.100.42:
    Packets: Sent = 4, Received = 4, Lost = 0
    (0% loss),
Approximate time in milliseconds:
    Minimum = 4ms, Maximum = 10ms, Average = 6ms


Excerpt from the OpenVPN client log:
⏎[Oct 26, 2025, 11:11:02] Connected via TUN_WIN
⏎[Oct 26, 2025, 11:11:02] EVENT: CONNECTED vpn.***@192.168.2.230:1194 (192.168.2.230) via /UDP on TUN_WIN/10.99.99.2/ gw=[10.99.99.1/] mtu=1500⏎

I am grateful for any response, because I am slowly running out of ideas as to what the problem could be or what I can do.