How to make a website for 2 providers?

Question

linux

Good afternoon! There was such a question and complexity. In general, I'm trying to implement such a thing when 1 site hangs immediately on 2 Internet providers
. However, I don't fully understand how to set up routes on the server here. From what is at the moment: everything works from 1 subnet, the site opens from the outside. No from the second subnet: the request does not reach. More precisely, it reaches the server, but does not reach further. And there is no access to the world from the second subnet either. So I understand that the matter is in default gw, however, I can’t assign 2 defgw? and if so, how will it determine which interface the request came from?

Answer 1

On a machine with a Linux site? Providers come from two different routers?
then just read how to send packets back to the same interface they came from. Google for iproute2 and multihome.
Here is a good link right away, https://habr.com/en/post/107267/

Answer 2

Where exactly and from where does the request not reach the second subnet? Try to catch the packet on the webserver side and track the direction of the response. default gw only affects connection initialization from the server. All incoming connections work according to the rules "from where I came there and back" if there is no explicit processing on the side of the firewall.

Answer 3

In general, I'm trying to implement such a thing when 1 site hangs immediately on 2 Internet providers

And how will customers find out through which provider it is better for them to open a site? Here, in addition to the obvious (setting up sending response packets through the same interface, we already wrote about this above), you need to provide for the slipping of the correct DNS records - otherwise users may come across an option that is less advantageous in terms of network topology.
Or are you doing it purely for fault tolerance? Then it is necessary to provide for cutting out one of the A-records in case of failure of one of the providers.
Everything is very difficult, in short (c)