Mikrotik: Routing exact IP thru VPN?

Question

I have the following setup:

Linux server running OpenVPN Server. It has full access to the Internet and public IP 1.2.3.4. OpenVPN uses tun0 and static IP 10.8.0.1
Mikrotik hEX lite (i don't think the model really matter). It also has a full access to the Internet, but it's behind some other, uncontrolled router. It's connected to OpenVPN server via myvlan, IP 10.8.0.2.
OpenVPN tunnel is active, i can ping each other, using 10.8.0.*

I'm trying to route traffic from linux server to 100.1.1.1 through VPN tullel to Mikrotik and then to the internet, like shown on the picture. So I have route add 100.1.1.1 via 10.8.0.2 dev tun0 on linux server:

$ ip route get 100.1.1.1
100.1.1.1 via 10.8.0.2 dev tun0 src 10.8.0.1 uid 1000
    cache

But I have lack of knowledge, what should I do on Mikrotik side? I thought that default masquerade aka "scrnat everything to Out. Interface List = WAN" would be enough, but I was wrong.

Network map

Actually I run something like this for one customer, just it is not OpenVPN because its support on the Mikrotik is, honestly, *worse than nothing*. Basically you are doing all correct, you need some kind of SNAT on the mikrotik side, for replies to be directed to it. Probably it didn't worked probably due to some caching by the Mikrotik, try cleaning connection tracking, route caches before retry. — Nikita Kipriyanov, Mar 02 '21 at 10:08
Did you tried to capture your traffic (at least, use *torch* on involved interfaces)? What it shows? — Nikita Kipriyanov, Mar 02 '21 at 10:57
Is your route in "Active" state? I mean, does "sending" mikrotik really send packets into VPN interface? — Nikita Kipriyanov, Mar 03 '21 at 05:33
Well, i can ping 10.8.0.1 from mikrotik, so yes, it's active — yegorov-p, Mar 04 '21 at 08:24
Ok, this is good, and if you ping 100.1.1.1 do Mikrotik see packets? — Nikita Kipriyanov, Mar 04 '21 at 08:27
Yes, sure. 100.1.1.1 is reachable from Mikrotik and i am sure that the tunnel also works — yegorov-p, Mar 04 '21 at 12:39

Mikrotik: Routing exact IP thru VPN?

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