Hello, check the ttached file.
I have a host in 192.168.3.x and another in 192.168.4.x
Both conect to same server with 2 interfaces ending in .254
I have no iptables rules, i activated /proc/sys/net/ipv4/ipv4_forwarding to 1
The host 192.168.3.3 can ping 192.168.3.254 but not 192.168.4.254
The host 192.168.4.4 can ping 192.168.3.254 and can ping 192.168.4.254