Firewall Versus Filters; Applying A Filter; Figure 69 Protocol And Device Filter Sets - Nortel 252 Configuration

150 Chapter 11 Filter configuration
are replaced on a connection-by-connection basis, which makes it impossible to
know the exact address and port on the wire. Therefore, the Business Secure
Router 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 Business Secure Router is
receiving and sending the packets; for example. the interface. The interface can be
an Ethernet port or any other hardware port, as illustrated in

Figure 69 Protocol and Device Filter Sets

Firewall Versus Filters

Firewall configuration is discussed in
page 131
filtering, NAT and the firewall.

Applying a Filter

This section shows you where to apply the filters after you design them. The
Business Secure Router already has filters to prevent NetBIOS traffic from
triggering calls, and block incoming Telnet, FTP and HTTP connections.
NN47923-501
chapters of this manual. Further comparisons are also made between
Note: Nortel recommends that you apply filters if you do not activate
the firewall.
Chapter 10, "Introducing the firewall," on
Figure 69.