Operating instructions

Reference Manual for the Model DG834 ADSL Firewall Router
Protecting Your Network 4-9
Considerations for Inbound Rules
• If your external IP address is assigned dynamically by your ISP, the IP address may change
periodically as the DHCP lease expires. Consider using the Dynamic DNS feature in the
Advanced menus so that external users can always find your network.
• If the IP address of the local server computer is assigned by DHCP, it may change when the
computer is rebooted. To avoid this, use the Reserved IP address feature in the LAN IP menu
to keep the computer’s IP address constant.
• Local computers must access the local server using the computer’s local LAN address
(192.168.0.11 in the example in Figure 4-6 above). Attempts by local computers to access the
server using the external WAN IP address will fail.
Outbound Rules (Service Blocking)
The DG834 allows you to block the use of certain Internet services by computers on your network.
This is called service blocking or port filtering. You can define an outbound rule to block Internet
access from a local computer based on:
• IP address of the local computer (source address)
• IP address of the Internet site being contacted (destination address)
•Time of day
• Type of service being requested (service port number)
Following is an application example of outbound rules: