for school we have to do a linux routing vm between 4 subnet but the routing only works in one way. Let me explain, here is a schematic:

[![enter image description here][1]][1] [1]: https://i.sstatic.net/tXBnA.png

The router in the center is a CentOS 7 fully up-to-date with 4 nic, each one in a different subnet:
10.1.21.151/24 (top) -> lan of client pc and esxi server.
200.200.0.254/24 (left) -> lan of a first windowsServer2016 AD/Exchange
200.200.1.254/24 (bottom) -> lan of a nagios server
200.200.2.254/24 (right) -> lan of a second windowsServer2016 AD/Exchange
The default gateway is 10.1.21.254/24

After enabling ip forwarding in centOS, I can access the nagios web interface from my client so the routing in that way is ok.

But with the nagios server, when i try to quit his subnet and ping my client, esxi, windowsServer1 or 2 -> nothing

Since the router has access to all subnet directly, i did not create any static route. Am i wrong ?

I think it isn't a routing problem but a "software" problem... Firewalld and NetworkManager are disabled.

Could someone help me ?

Hope that i did not make too many mistakes, native french speaker :D

Thanks