ZyXEL Communications Broadband Security Gateway P-312 - Manual (Page 112)

P312 Broadband Security Gateway
Filters 7-17
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 Prestige is receiving and
sending the packets; i.e. the interface. The interface can be an Ethernet port or any other hardware port. The
following diagram illustrates this.
Figure 7-15 Protocol and Device Filter Sets
7.5 Firewall
Firewall configuration is discussed in Part 4 of this manual. Further comparisons are also made there
between filtering, NAT and the firewall.
7.6 Applying a Filter and Factory Defaults
This section shows you where to apply the filter(s) after you design it (them). Sets of factory default filter
rules have been configured in Menu 21 to prevent NetBIOS traffic from triggering calls, and block
incoming telnet, FTP and HTTP connections.
If you do not activate the firewall, it is advisable to apply these default filters as
shown next.
7.6.1 LAN traffic
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, e.g., 3, 4, 6, 11. Input filter sets filter incoming traffic to the Prestige and Output filter sets filter
outgoing traffic from the Prestige. The factory default set, NetBIOS_LAN, can be inserted in protocol
filters –field under Input Filter Sets in Menu 3.1 to block NetBIOS traffic to the Prestige from the LAN.