I thank you for your answer.
My English is not good either, and all the automatic translators are not perfect.
But I think I understand.
My particular network configuration is related to the fact that I change it all the time for testing.
Apart from an OpenVpn server installed in IPFire (which I only connect to from outside), I have nothing else. I am the only user on my network.
As a result, I have no problem experimenting. I like IPFire precisely because I can study and understand it.
In the normal condition, a network like mine should simply be
192.168.1.0/255.255.255.0
I didn’t think about the DHCP issue you raised.
My ideas about DHCP are fruits of testing, but not of study. And therefore, I am not sure what I stated about the DHCP server. Reading what you told me, I became curious to look into the subject further. That’s all.
I will certainly do more experiments on my network, experiments that I avoid in case the network does not belong to me 
.
The URL filter is vital for me when I receive children at home 
.