Chapter 12 Packet Filter
P-79X Series User’s Guide
125
12.3 Packet Filter Technical Reference
This section provides some technical background information about the topics covered in this
chapter.
12.3.1 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 P-79X 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 P-79X 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 73 Protocol and Generic Filter Sets
Value Enter the value (in hexadecimal notation) to compare with the data
portion.
More Select Yes to pass a matching packet to the next filter rule before an
action is taken.
Select No to act upon the packet according to the action fields.
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.
Table 46 Security > Packet Filter > Edit (Generic Filter) > Edit Rule (continued)
LABEL DESCRIPTION
Protocol
Filters
Generic
Filters
NAT
Interface
Route
Incoming
Outgoing
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