ZyXEL Communications ADSL 2+ Gateway P-660HW-T1 - Manual (Page 281)

P-660H/HW/W-T Series User’ Guide
281 Chapter 29 Filter Configuration
29.5 Filter Types and NAT
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 173 Protocol and Device Filter Sets
29.6 Example Filter
Let’s look at an example to block outside users from telnetting into the Prestige.
Log Select the logging option from the following:
None – No packets will be logged.
Action Matched – Only matching packets and rules will be logged.
Action Not Matched – Only packets that do not match the rule parameters will be
logged.
Both – All packets will be logged.
Action
Matched
Select the action for a matching packet. Choices are Check Next Rule, Forward or
Drop.
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 97 Menu 21.1.5.1 Generic Filter Rule (continued)
FIELD DESCRIPTION