How to set up mikrotik for three internets?

Question

DHCP

There is a Mikrotik RB951UI-2ND router, capable (and only for this reason acquired) of distributing three Internets at once:
1) "First" (wan-1) connection - comes via DHCP. It is necessary to re-distribute (I forgot the name of this mode) this DHCP to the entire network behind Mikrotik to all ports except the second one (there is wan-2).
2) "Second" (wan-2) connection, for the activation of which it is necessary to prescribe static parameters. Needed by only one computer (pc1).
3) "Third" connection - 3G whistle - backup. necessary during failure of the "second" connection. That is, if the "second" connection fails, pc1 should not notice a drop in the Internet (there is a video broadcast on it) and should automatically receive an Internet stream from the "third" connection.
Rattlesnake question ... how to set it all up? Suddenly, someone has a ready-made configuration or ... at least poke into a specific mana :)

Answer 1

1) DHCP Relay
2) google://mikrotik+policy+based+routing
3) normal default setting

Answer 2

There is a Mikrotik RB951UI-2ND router, capable (and only for this reason acquired) of distributing three Internets at once:
1) "First" (wan-1) connection - comes via DHCP. It is necessary to re-distribute (I forgot the name of this mode) this DHCP to the entire network behind Mikrotik to all ports except the second one (there is wan-2).
You will need to remove ports 3,4,5 from master-port . Assign master port 3 to port and make slave ports 4 and 5.
Ports 1 and 2 will no longer be tied into a bridge.
2) "Second" (wan-2) connection, for the activation of which it is necessary to prescribe static parameters. Needed by only one computer (pc1).
Well, the second PC, where will it connect?
3) "Third" connection - 3G whistle - backup. necessary during failure of the "second" connection. That is, if the "second" connection fails, pc1 should not notice a drop in the Internet (there is a video broadcast on it) and should automatically receive an Internet stream from the "third" connection.
Do you understand that miracles do not happen?
If you have a failure, then you still need time to
1) switch
2) to restore the data flow, since there will be a new ip address
With Mikrotik reservation out of the box at the gateway check level. Those if suddenly the provider's gateway is alive, but there is no Internet (did not pay), then there will be no switching.
To make the switch, you need to write scripts that will determine whether the Internet is alive by pinging several selected sources.
as an option, they recently washed down - https://wiki.mikrotik.com/wiki/Manual:Detect_internet
Just for your topic, but I personally have not used it yet.
You will also need to mark traffic in order to let different machines go to different Internet.

Answer 3

This is not a bad article. Based on this article, it is quite possible to set up all your "Wishlist".

Answer 4

https://www.youtube.com/watch?v=T_3mWxAYBL0