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Configuring Your Gateway
77
SMCD3GN-RRR Wireless Cable Modem Gateway User Manual
Option
Description
IP Replacement
Select the IP replacement according to the application. Some applications embed the source
host's IP in the datagram and normal NAT would not translate the IP address in the datagram.
To make sure the network address translation is complete, IP replacement is necessary for
these special applications, such as H.323.
Allow sessions initiated from/to the
3
rd
host
Decide whether the sessions can start from/to a third host. To prevent hacker attacks from a
third host, this feature usually is not allowed. However, for some special applications, such as
MGCP in a VOIP application, a session initiated from a third host is permitted. For example,
assume Client A is trying to make a phone call to a host B. Client A tries to communicate with
the Media Gateway Controller (MGC) first and provides host B's number to MGC. Then MGC
checks its own database to find B and communicate with B to provide B the information about
A. B uses this information to communicate directly to A. So initially, A is talking to MGC, but
the final step has B initiating a session to A. If the third-party host-initiated session is not
allowed in this example, the whole communication fails.
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Using the URL Blocking menu, you can configure your Gateway to block access to certain
Web sites from local computers by entering either a full URL address or keywords of the
Web site. your Gateway examines all the HTTP packets to block the access to those
particular sites. This feature can be used to protect children from accessing inappropriate
Web sites. You can block up to 50 sites.
Using URL blocking, you can also make up to 10 computers exempt from URL blocking and
have full access to all Web sites at any time.
To display the URL Blocking menu, click
Firewall
in the menu bar and then click the
URL
Blocking
submenu. Figure 45 shows an example of the menu.
Note:
The
URL Blocking
submenu is not available in the menu bar if
Enable Firewall
Module
is disabled in the Security Settings (Firewall) menu (see page 67).
Tip:
The Gateway provides a Schedule Rules feature that lets you configure URL blocking for
certain days, if desired. For more information, see “Configuring Schedule Rules” on page 79.