I’m sorry, my bad: your configuration does not have a red interface! However it is really complex!
IIUC you have two green networks and need to communicate with other networks behind a VPN router…
At the moment, the nsdc network configuration sets the green network gateway as default (and unique) route. That gateway is the only responsible for all packet routing rules.
We are planning to set NethServer itself as gateway, if a red interface is present. This scenario is still not covered by our configuration and needs to be fixed.
Meanwhile I’d move forward with the original problem:
NethServer has a modular design and is often considered an all-in-one server. It’s perfectly fine to install all modules on a single system, however if something is not working properly it’s more difficult to debug.
Some people prefer to split the roles across different machines, expecially firewall and everything else.