How to organize a fault-tolerant VPN connection (Mikrotik)?

Question

VPN

Good afternoon.
There is a need to organize the smooth operation of office and remote employees.
The initial data is as follows:
OFFICE_1

• GW01 Router Mikrotik RB750Gr3 172.10.100.1/24
  
• ISP1 has an external static address of 1.1.1.1
  
• ISP2 has gray address 192.168.10.10
  

OFFICE_2

• GW02 Router Mikrotik RB750Gr3 172.20.100.1/24
  
• ISP1 has an external static address of 2.2.2.2
  
• ISP2 has gray address 192.168.20.20
  
• terminal server
  

Now everything is organized as follows: An L2TP server is configured on GW01 , GW02 connects to it as a client, behind which a terminal server is located. Thus, employees from OFFICE_1 can work with the server. If the main provider ( ISP1 ) is unavailable , all VPN clients disappear on GW01 .
Actually, this and all the question is how to implement a backup channel for VPN? Whether it is possible to solve a question without the static address on ISP2 ?
I would be grateful for any solutions and tips.

Answer 1

You raise 2 VPN channels
GW01 ISP1 - GW02 ISP1
GW01 ISP2 - GW02 ISP1 You configure
inside OSPF, it will switch routes itself depending on the availability of VPN channels.
LT2P is not the best performance option, try IPsec.

Answer 2

Raise the opposite L2TP from ISP2_GW01 to ISP1_GW02 and scatter priorities with metrics

Answer 3

And where to send packets if there is no address on the Internet?
You can, of course, sandwich a variant with a virtual machine somewhere on the internet with a white address and a channel that is built by Mikrotik to it through ISP2. But the provider's white address is easier in my opinion :)