How to correctly build a network topology in a building?

Question

Network administration

In general, two 100 Mbps fast ezernets are connected to the office building to two Wi-Fi routers. On one - one network, on the other - another. They are not united in any way.
In the first network, terminal devices (PCs and Wi-Fi clients) and another router that connects some of its terminal devices are connected to a router with Internet access.
In the second network, terminal devices and two more routers are connected to the router with Internet access, to which some terminal devices are connected.
All routers are wi-fi, all have wi-fi clients. On all routers, except for two with Internet access, nat and dhcp are disabled by enabling access point mode.
IPs in such a network are issued by dhcp servers of routers that have access to the Internet.
So that's the question itself ... How can you combine and configure these networks in such a way that you can locally access any computer from any computer? What is the best way to implement network subnetting? How to make sure that when connecting to a specific router via Wi-Fi, the client gets into the right subnet (for example, when connecting to a router in the IT department, a person gets into the subnet of the IT department)?

Answer 1

Combine networks either by wire between head routers, or vpn via fast ethernet. You can, of course, also have a wifi bridge, but IMHO there will be problems, especially with a more or less decent load.
Access between networks by ip addresses is determined by routing tables and firewall rules.
Subnets on routers can be scattered either using DHCP on them, or using options 82.
You can also steer all this using a RADIUS server.
For more or less normal access by name, you need to configure the DNS server, I don’t know if your routers can do it.
Subnetting to do depending on the requirements for routing. Judging by "for example, when connecting to a router in the IT department, a person enters the subnet of the IT department," you should have them, and that's what you need to start from. The only thing is that it’s easier to do everything statically, and for each router to allocate an independent network of sufficient size, and divide it as necessary. Although no one forbids linking an ip address to a device and let it walk on routers as it wants, but this is difficult and IMHO is not necessary.