Chapter 32 Filter Configuration
P-792H v2 User’s Guide
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Translation) is enabled, the inside IP address and port number are replaced on a
connection-by-connection basis, which makes it impossible to know the exact
address and port on the wire. Therefore, the P-792H v2 applies the protocol filters
to the “native” IP address and port number before NAT for outgoing packets and
after NAT for incoming packets. On the other hand, the generic, or device filters
are applied to the raw packets that appear on the wire. They are applied at the
point when the P-792H v2 is receiving and sending the packets; in other words the
interface. The interface can be an Ethernet port or any other hardware port. The
following diagram illustrates this.
Figure 185 Protocol and Device Filter Sets
32.5 Firewall Versus Filters
Firewall configuration is discussed in Chapter 10 on page 149. Further
comparisons are also made between filtering, NAT and the firewall.
32.6 Applying a Filter
This section shows you where to apply the filter(s) after you design it (them). The
P-792H v2 already has filters to prevent NetBIOS traffic from triggering calls, and
block incoming telnet, FTP and HTTP connections.
Note: If you do not activate the firewall, it is advisable to apply filters.
32.6.1 Applying LAN Filters
LAN traffic filter sets may be useful to block certain packets, reduce traffic and
prevent security breaches. Go to menu 3.1 (shown next) and enter the number(s)
of the filter set(s) that you want to apply as appropriate. You can choose up to
four filter sets (from twelve) by entering their numbers separated by commas, for
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