OpenVPN Net2Net Performance bad

[gtrdriver]

Hello

sorry for doing a Crossposting - but on the german part of this board i dont get a answer so i try it here…

First of all - i have a test System for testing Performance of FW and Openvpn systems.

Server1: is within a Datacenter with dedicated 500mbit Connection to the Internet (Hypervisor fast hardware Firewall as Gues OS)
Server2: is at a Dialup VDSL Line with 50/10mbit - also fast hardware also Hypervisor and Firewall as Guest OS

The Goal is a NEt2NET Connection with VPN to connect 2 Subnets

My First tests i did with IPFIRE and OpenVPN and first tests show me a down Rate about 25mbit/s and Up Rate about 8mbit/s.
After doing some Research and set TUN MTU to 1500 + Forece MTU Discover i get 48mbit Downstream and 9,5 Upstream over VPN so nearly the MAX Bandwith of the Connection

(all Meassured with iperf)

But i dont like IPFIRE and want to use IPSENSE)

But wit Ipsense i dont get more then 28mbit down and 8mbit up - even when i switch off Encryption .....

I also dont find any way to adapt MTU Discovery or other Tewaks

i Searcht on the Net for the last 3 Days for solutions - i did some test with the Advanced Options - but still have this bad Performance.

Can anyone help me ?

Best Regards