ZyXEL Communications P-660 series Guia do Utilizador descarregar pdf (Página 112)

Chapter 8 Packet Filters

P-660R-F1 Series User’s Guide

112

8.3 Packet Filter Technical Reference

This section provides some technical background information about the topics covered in this

chapter.

8.3.1 Filter Types and NAT

There are two classes of filter rules, generic filter rules and protocol filter rules. Generic filter rules

act on the raw data from/to LAN and WAN. Protocol filter rules act on the 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 ZyXEL Device 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 filters are applied to the raw packets that appear on the wire. They are applied at the

point when the ZyXEL Device is receiving and sending the packets; that is the interface. The

interface can be an Ethernet port or any other hardware port. The following diagram illustrates this.

Figure 69 Protocol and Generic Filter Sets

8.3.2 Firewall Versus Filters

Below are some comparisons between the ZyXEL Device’s filtering and firewall functions.

Log Select a logging option from the following:

None – No packets will be logged.

Match - Only packets that match the rule parameters will be logged.

Not Match - Only packets that do not match the rule parameters will be

logged.

Both – All packets will be logged.

Action Match Select the action for a matching packet.

Options are Check Next Rule, Forward and Drop.

Action Not Match Select the action for a packet not matching the rule.

Options are Check Next Rule, Forward and Drop.

Back Click this to return to the previous screen without saving.

Apply Click this to save your changes.

Cancel Click this to restore your previously saved settings.

LABEL DESCRIPTION

Protocol

Filters

Generic

Filters

NAT

Interface

Route

Incoming

Outgoing

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ZyXEL Communications P-660 series Guia do Utilizador Página 112