Why is the Internet speed low through l2tp+ipsec client which is configured on Mikrotik?

Question

VPN

Hi all.
There is a VPS server in Europe with Ubuntu 18.04 installed. VPN server l2tp+ipsec is configured on this server.
The office has Mikrotik RB4011iGS +, it has an l2tp client configured that connects to the VPN server. Everything seems to work, but there is a problem that the speed of the Internet connection is very low, up to 0.17Mbit. But when I just do the configuration directly through Windows 10, the speed is normal from 60 to 80Mbit.
What could be the problem?
I made the server config according to this article: https://www.mytechnote.ru/article/borba-s-blokirov...

The Mikrotik config is standard, set up the interface itself, made nat, mangle and routes, also added an address list to separate users who are on the VPN and those who are from the provider's IP

VDS Server Provider Speed: 100Mbps
Office Provider Speed: 1Gbps
X VPS: 4CPU, 4RAM, 80Gb SSD.

Answer 1

Wow... are you going to calculate nuclear models there?))
Either the provider even cuts (for example, the speed to Europe) well, or the TSPU does not have time to decrypt the traffic))
Or check the CPU load of the mikrotik
Try pptp or openvpn
I have RT it was such a hoot. Until I set up openvpn with my certificate on port 443 - the speed was cut to zero (

Answer 2

Try IPSec / IKE2, on the same 100Mb channel on Mikrotik, the speed shows 95Mbps.

Answer 3

Try to set Max MTU on the client to 1400 and compare the speed. And generally test different MTUs.