ZyXEL p-662h-61 Guia Do Utilizador

Prestige 662HW Series User’s Guide

371

Chapter 36 Filter Configuration

There are two classes of filter rules, Generic Filter Device rules and Protocol Filter (TCP/IP) 
rules. Generic Filter rules act on the raw data from/to LAN and WAN. Protocol Filter rules act 
on IP packets.

When NAT  (Network Address 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 Prestige 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 where the Prestige is receiving 
and sending the packets; for instance, the interface. The interface can be an Ethernet, or any 
other hardware port. The following figure illustrates this.

Figure 214   Protocol and Device Filter Sets

Let’s look at an example to block outside users from telnetting into the Prestige. 

Action Not 
Matched

Select the action for a packet not matching the rule. Choices are Check Next Rule, 
Forward or Drop.

When you have completed this menu, press [ENTER] at the prompt “

Press ENTER to Confirm 

or ESC to Cancel:

”  to save your configuration, or press [ESC] at any time to cancel.

Table 128   Menu 21.1.5.1 Generic Filter Rule (continued)