Why is the Internet not available on the subnet?

Question

System administration

There are two Mikrotik as in the picture. Both Mikrotiks are geographically in the same building, but far from each other. Both Mikrotiks have their own internets. It is necessary that Internet is available on Mikrotik 1, which is provided by Mikrotik 2.
When I ping any Internet address on the eth5 interface of Mikrotik 1, then pings do not go. Although I set everything up as needed - I assigned subnet addresses 172.16.255.0 to both Mikrotiks. In NAT, Mikrotik 2 set up a masquerade:

/ip firewall nat
add action=masquerade chain=srcnat out-interface=eth0

In general, I would like Miroktik 1 to have two Internets. If Mikrotik 1 has Internet 2.3.4.5, then the Internet from Mikrotik 2 will turn on.
Please help me figure it out ..

Answer 1

If, simply, without checking the availability of the Internet, not through the provider's gateway, then you should have two default routes (0.0.0.0) on Mikrotik 1:
1. 0.0.0.0 through 2.3.4.5 c distnace 1
2. 0.0.0.0 through 172.16 .255.2 distnace 2
Both check gateway ping
masquerade packets for the eth0 outgoing interface
Microtrick 2 should have a route to the 192.168.100.0/24 network via 172.16.255.1, well, masquerade for the eth0 interface

Answer 2

Make the default gateway switch when the main link goes down

Answer 3

You can do so.

Answer 4

You need to look at the routing table.
I have several questions at once:
1) why then the second Internet?
2) why not hang a second Internet on one router and make it the main one?
3) why do you need another extra network 172 and even with a mask / 24 for connecting routers? or is there something else?
As a result, it is necessary to register routing between networks 100.0 and 200.0.
Remove NAT on mikrotik 1, specify default route mikrotik 2 router.