DHCP Relay
You can enable relaying of DHCP requests to a server on a different network. The DHCP relay only forwards DHCP requests between the server and the clients. In some DHCP implementations, when a client has received an IP address from the DHCP server, it needs to communicate with the server regularly to keep the leased address. This communication is not sent via the relay, which means that you have to define a firewall rule for this traffic. This is done on the Rules page.
Many DHCP servers and clients try to send ping requests to the IP address that is allocated. Then a rule is needed to allow ping requests from the server network to the client network.
Many DHCP servers also want to look up the IP address to be leased in the DNS. In that case, that traffic too must be allowed from the DHCP server to the DNS server.
If you don't know what kind of traffic the server will send, you can create rules for all the alternatives stated above. If the server doesn't need them, nothing else will happen. You could also check the log to see if they are used.
DHCP relay status
Here, you select whether the DHCP relay should be ON or OFF.
Clients are directly connected to interface
The computers making DHCP requests are called clients. The DHCP relay can only relay requests from one of the firewall's interfaces. Here, you select the firewall interface to which the clients are connected.
DHCP server
Here, you enter the IP address of the DHCP server.
The DHCP server can be connected to any of the firewall's interfaces. As the firewall knows which IP addresses are connected to each interface, you don't have to select an interface here.
The relay port number for sending and recieving
Here, you enter which port number the DHCP relay should listen and send to. Usually, DHCP uses port 67.
Save
Saves the DHCP Relay configuration to the preliminary configuration.
Undo
Reverts all of the above fields to their previous configuration.