How to organize the connection of local networks through several channels?

Question

Computer networks

There are:
1) 2 local networks in different offices - 192.168.10.0/24 and 192.168.100.0/24
2) a direct physical ethernet connection between them (RRL works as a switch)
3) a provider's network with addresses, suppose in the first office 10.1.0.2, in the second 10.1.0.3
4) the network of the second provider with addresses, let's say in the first office 10.2.0.2, in the second 10.2.0.3 It is

necessary to organize uninterrupted access from the networks of one office to another using RRL as the main channel and two backup from providers with automatic switching between them

What equipment is needed for this based on the minimum budget
read about VPN networking through routers and using a router to make networks available via RRL

Answer 1

PCs with Linux or Free BSD, routers with OpenWRT, microtics, etc. will do - choose from the budget, availability of operating experience, and so on.
The technology is called "dynamic routing". I did this using OSPF in a similar situation, only the network was not RRL, but optics.
Put two routers at the ends of the connection, make a VPN if necessary, then configure dynamic routing on top of the VPN - as soon as OSPF sees the second router through one of the connections, it will choose (according to the configured weight) which routes to enter in the routing table.

Answer 2

1. Put normal routers in both branches. (Mikrotik, BSD, WRT, PF or something similar)
2. The external address of at least one of the offices must have a white IP to configure the VPN gateway (well, or if at both ends one provider orders a ready-made VPN point-to-point ")
3. Set up this VPNa channel - the network is full of instructions
4. RRL data would also not hurt to tunnel in reserve, so we are also building a direct point-to-point VPN.
5. you combine the resulting 2 channels into dynamic routing, (there are also enough instructions about combining networks over two channels)
6. you can also prodynamize 0.0.