How to organize switching of services with two or more providers?

Question

Nginx

Good afternoon!
We have two providers (main - fast and backup - slow) Internet and MikroTik implements switching from one provider to another when the main channel disappears - this works without problems.
The problem is that we still have services sites, vpn, etc. and when switching, they do not work because the dns record refers to the first provider. If you manually rewrite the records, then the switching is slow until the dns roll out.
How to implement instant switching?

Answer 1

1) Prescribe dns to both addresses, the call will always be at available addresses, i.e. if only channel 1 works - access will be through it, if only channel 2 works - access through it.
2) Proxy through cloudflare or your VPS, only suitable for websites.
3) (best option) Buy an ASN, a pool of your addresses and connect to providers via BGP

Answer 2

I support the first answer from Wexter. Only with the organization of the work of all services through two providers simultaneously with balancing by priority (you have a microt). Organize dns balance by standard solutions, also by priority.
Your AS through BGP is, of course, specific and on target, but brbrbr, don't you think it's too cool? And it costs money. The task is solved by the forces of the router and I will note for free. If he has enough resources.
ZY If there are questions "how?" write in private. I will write personally, but there are a lot of answers in the open spaces.

Answer 3

BGP
AS is rented from a big guy, your provider, if it is thick enough (any of them), will easily give you a lease and help you set it up. But, depending on the Mikrotik model and on your fullview decision, you may have to change the Mikrotik to a more productive model.
You can buy ASku, but it will be more difficult.

Answer 4

Normally, only BGP with its own block of addresses / ASN or external hosting. Life hacks:
1) two different domains to different addresses, for example eth0.example.com and lte0.example.com. It is unlikely that in the event of a FOCL break, a bunch of remote clients will go to lte.
2) an external server with a static address, a couple of tunnels to it from your location, traffic routing through the server (if the traffic to the site is small).
3) v6 for external services
4) If the number of users is limited, you can start a separate DNS server with a low TTL, users can register this DNS in their own.

Answer 5

An advanced router should have dynamic DNS, DynDNS. Try it.
However, I'm not sure that it will be "instantaneous switching".

Answer 6

Wexter is correct. But you can slightly reduce the problem "switching is slow until dns rolls out" by specifying a smaller TTL at the DNS server