Connecting two networks (each with separate internet connection)

Question

Here is my network diagram:

This image might need a little explanation.

I am currently in charge of unificating a multi-network environment in a small business. I am the first hired IT Admin, and apparently my "predecessor" (who was not entirely aware of what he was doing) decided it would be a good idea to have three seperate wireless networks, each broadcasted by their own router. Given that there are two internet connections in the building, there's two routers directly connected to a modem. The third router was placed right behind one of those other routers, yet was configured to set up it's very own network.

The first step in that unification was simple enough, since one router was behind another, I turned the inner router into an access point. In the linked image, this is called the "Access Point Administration" which is connected to the router.

The second step, I am having a bit of doubts. I need to be certain before I proceed to avoid problems with people losing internet connection.

The "Access Point Vendor Space" as shown in the image is at this time still set as router creating its own network. In order to turn that into an access point, I need to create a link between this access point and the router in the first network, to ensure that all clients can get their IP's assigned. However for practical reasons it is impossible to connect these two devices directly. So hence my questions:

1. Would the green link between the "Switch Floor 2 (15B)" and "Switch Floor 2 (15A)" result in a valid internal network with the Router as DHCP server and the device in the Vendor Space as an Access Point? I would think the answer is yes since this connection creates in fact a direct link between both devices, given that Switches don't "route" traffic but keep MAC addresses for immediate forwarding. Therefor in my understanding, all users would be forwarded to the Router and be assigned their IP-addresses, and in addition use this Router for their internet connection.

2. Presuming the answer to the first question would be yes: it would obviously not be optimal for the users connected to the "Access Point Vendor Space" or the "Switch Floor 1 (15A) to connect to the internet through the Router, especially since there is an internet connection closerby at the "Access Point Vendor Space". Hence the question: is setting the Default Gateway of these users to the IP address of the "Access Point Vendor Space" a correct way to achieve this; is there not a more general way to achieve this by configuring at the Access Point?

Thanks beforehand!

Answer 1

I will answer my own question, just in case anyone ever wonders about a similar networking problem.

1. It is indeed possible to connect these two networks at that level. It results in a valid network - as long as there is only one DHCP server of course. All the other devices with this capability should have the DHCP server function turned off and should instead operate as if they were a switch (or a wireless hotspot).

   More generally, it is possible to connect two networks at any desired "level" of depth, as long as no circle is created within the network's construction. In the given example, an invalid network would occur by, in addition to the green arrow, creating a connection between Switch Floor 1 (15B) and Switch Floor 1 (15A). The circle would be Switch Floor 1 (15B) -> Switch Floor 1 (15A) -> Switch Floor 2 (15A) -> Switch Floor 2 (15B) -> ...

2. Although I have decided to use only one internet connection, it is indeed possible to configure specific computers to use the "secondary" internet connection. This can be done by changing each computer's network configuration individually: simply insert the IP-address of the router with the secondary internet connection as Default Gateway for that computer.