How to make simultaneous access from outside through two WANs?

Question

Computer networks

Good afternoon.
Two providers are connected to the Mikrotik router:

A (46.46.46.46) - main, statics, metric 1;
B (58.58.58.58) - reserve, DHCP, metric 2;

There is a local network 192.168.1.1, the network has a server 192.168.1.25 to which RDP (3389) is forwarded.

When ISP A is the default gateway, the server is reachable from outside on
both 46.46.46.46:3389 and 58.58.58.58:3389.
But when I set provider B as the default gateway, the server is available only at 58.58.58.58:3389.

Why in the second case it is impossible to go to the server through two channels, but in the first case it is possible?

Answer 1

Because pbr is not configured. Apparently, one of the providers calmly forwards the left src-ip from you, and the second one cuts them.
Configure pbr so that server responses from the address 46.46.46.46 go only to the first channel, and 58.58.58.58 to the second.

Answer 2

Perhaps the pbr is not configured correctly. Need more information (at least router config)

Answer 3

reserve, DHCP, but you also need static, because it is not clear what is assigned to the 1.25 server, or the routes are not correctly rebuilt

Answer 4

Because the default route, when you try to connect through the second provider, the answers are sent to the first one, where no one is waiting for them. You make 2 IPs on RDP and let each IP go through one provider.