How to organize a network between enterprises?

Question

VPN

I can imagine how to do it in theory, but when the moment came and you need to do it in practice, a lot of nuances arose. Perhaps you can guide me on the right path.
I would not like to rent a server, but to solve the problem in my hardware locally.
Given:
- two offices
- both have one provider
- the provider's internal network is 100Mbps
- both have a white dynamic IP (changes when the lights turn off fanlike)
Find:
- rdp connections
- 1c to the server
- internal resources
I would be very grateful for advice.

Answer 1

To each office via a router and VPN with tun or tap (if you want to distribute DHCP from one office to another. However, this is a bad practice).

Answer 2

If the addresses are white, you can connect via dyndns in one of the offices. Otherwise, you can buy a static white address (usually sold for legal entities). And then a couple of Mikrotiks / Linux PCs / more expensive routers and go ahead, network)

Answer 3

Call the provider and ask for l2vpn. It will be possible to refuse the Internet on one point. Vlans are cheaper than the Internet)