How to redirect traffic to an inaccessible server through another gateway?

Question

Mikrotik

There are 2 mikrotik connected by vpn tunnel. They are located in different countries, so different sites are available for them. The task is this: if a connection to some site is not established through an ISP, then you should try to connect through a vpn tunnel. It seems like it’s clear that traffic needs to be marked, but I don’t quite understand what the conditions for marking should be.

Answer 1

The logic is this - if the site is not available through R1, then we turn on the marking rule and the traffic is routed through R2.
You can script this using ping and fetch, and put it in the scheduler for regular checks or use netwatch. Marking conditions - dst address

Answer 2

Where are your main clients? And there and there, or just behind one of the Microts?