hello guyz to you all!!!
greeting from Greece, my name is Kostas and i am new to both the forum and to ipfire software…
i run ipfire arm 2.23.2version and i have it running for lab purposes on my local network build on a raspi 2b!
as you can see on my topology, after setting everything up correctly(i think so… 
)i get into a strange situation that the pc’s(end devices in the green network) cannot ping each-other(cannot ping DHCP server also) and also neither of those get a valid ipv4 address…i am able to connect to 192.168.31.100 on the red network and to see the web interface while i am on the 192.168.31.0/24 subnet but from the green i cannot log-on to the web interface at all…(ifconfig on the ipfire pi shows correct ip’s on both interfaces…)
can you suggest what is maybe wrong and how can i locate what is the problem?
The green interface shows a DNS of 192.168.31.100 Is that correct?
DNS may Ok but the gateway must be the green ip. But this is not the reason of a non working dhcp server. Is this really running. If IP / Netmask not match to the DHCP Range it will refuse to start.
Which exact version you are using (core, arch) ? IPFire 2.23.2 doesn’t exist!
I’m confused. In your graphic you show a static ip configuration for the clients, but you talk about a not working DHCP? Give them a static IP to test the accessability of ipfire.