Step 5: Test the Firewall

If the DHCP server was configured properly, then a PC or notebook computer can be connected into the same network hub to which the firewall’s GREEN interface is connected. The PC/notebook should get assigned the first available IP address that the Green connector’s DHCP server has available. For the demonstration machine, the assigned address was

Open a new browser instance and try navigating to a known website, like, or

If the firewall is working, then you should see the website contents. Yay!

If it is not working, then there are a number of areas to check:

  • Are the RED and GREEN adapters accidentally switched? If the Notebook/PC was properly assigned a network address, then they are correctly connected. If not, then try swapping the connections RED->GREEN and GREEN->RED by swapping the connection plugged into the network adapters.
  • Is the network hub plugged in and working? Most network hubs have lights on them to tell what is connected and communicating.
  • Is the RED interface actually properly configured? Sometimes the configuration requirements for connecting to the ISP modem are more complex than just letting it auto-configure using DHCP.
Firewall Status WAN-side
  • Is the GREEN interface properly configured? It should have a DHCP server assigning addresses on it.
DHCP Configuration


Additional troubleshooting assistance can be found online at the IPFire documentation.