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3G Broadband Wireless Router MBR624GU User Manual
3-8 Protecting Your Network
v1.0, January 2009
Considerations for Inbound Rules
If your external IP address is assigned dynamically by your ISP, the IP address might change
periodically as the DHCP lease expires. Consider using the Dynamic DNS feature so that external
users can always find your network.
If the IP address of the local server computer is assigned by DHCP, it might 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 previous example). Attempts by local computers to access the server using the
external WAN IP address will fail.
Outbound Rules (Service Blocking)
The router 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 the following:
• 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)
Outbound Rule Example: Blocking Instant Messenger
If you want to block Instant Messenger usage by employees during working hours, you can create
an outbound rule to block that application from any internal IP address to any external address
according to the schedule that you have created in the Schedule screen. You can also have the
router log any attempt to use Instant Messenger during that blocked period.