Network unreachable when I ping from internal network to another network

I installed IPFire as a virtual machine for a module in my studies under Oracle Virtual Box. In addition, I installed three virtual Ubuntu clients, too. The three Ubuntu clients are supposed to be located in three different networks (DMZ, internal network and customer network I had the red interface configured via DHCP because I want to use IPFire behind a router (Fritzbox). I use the network bridge to my WLAN network card as a connection setting for the red adapter under Virtual Box. My IPFire router can also go to the internet and ping requests to Google successfully.For all other network adapters from IPFire (green, blue and orange) I use fixed IP addresses, and I connected IPFire’s network adapters to the adapters of the virtual network clients via internal networks (intnet10, intnet20 and intnet30). I can ping any device from any network from the IPFire router. And any device on the network can also ping the router.However, I can’t access the Internet from the internal networks. In addition, I can’t ping devices from the other networks. Then I get the error message “Network is unreachable!”. I tried to figure out what’s going on through IPfire’s web interface. But I have no idea what could be going on. I hope you can help me :slight_smile: Regards from Angela