ZyXEL Communications Prestige 782R, User Manual, Page: 105 / 166

Prestige 782R G.SHDSL Router
Filter Configuration 8-15
When NAT/SUA (Network Address Translation/Single User Account) 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 Prestige applies the protocol filters to the “native” IP
address and port number before NAT/SUA for outgoing packets and after NAT/SUA 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 where the Prestige is receiving and sending the packets; i.e., the interface. The
interface can be an Ethernet, or any other hardware port. The following figure illustrates this.
Figure 8-10 Protocol and Device Filter Sets
8.5 Filter Configuration Example
Let us look at part of the third default ZyXEL filter as an example. See the Support CD for more sample
filters. This filter was designed to block outside users from telnetting into the Prestige.
Figure 8-11 Sample Telnet Filter