ZyXEL 202H 91-003-194001B User Manual
Product codes
91-003-194001B
P-202H Plus v2 User’s Guide
247
Chapter 25 Filter Configuration
Figure 148 Example Filter Rules Summary: Menu 21.1.3
This shows you that you have configured and activated (A = Y) a TCP/IP filter rule (Type =
IP, Pr = 6) for destination telnet ports (DP = 23).
IP, Pr = 6) for destination telnet ports (DP = 23).
M = N means an action can be taken immediately. The action is to drop the packet (m = D) if
the action is matched and to forward the packet immediately (n = F) if the action is not
matched no matter whether there are more rules to be checked (there aren’t in this example).
the action is matched and to forward the packet immediately (n = F) if the action is not
matched no matter whether there are more rules to be checked (there aren’t in this example).
After you’ve created the filter set, you must apply it.
1 Enter 11 from the main menu to go to menu 11.
2 Go to the Edit Filter Sets field, press [SPACE BAR] to select Yes and press [ENTER].
3 This brings you to menu 11.5. Apply a filter set (our example filter set 3).
4 Press [ENTER] to confirm after you enter the set numbers and to leave menu 11.5.
25.4 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 the IP packets. Generic and TCP/IP filter rules are discussed in more detail in the next
section.
IP) rules. Generic filter rules act on the raw data from/to LAN and WAN. Protocol filter rules
act on the IP packets. Generic and TCP/IP filter rules are discussed in more detail in the next
section.
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, or device 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; i.e. the interface. The interface can be an Ethernet port or
any other hardware port. The following diagram illustrates this.
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, or device 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; i.e. the interface. The interface can be an Ethernet port or
any other hardware port. The following diagram illustrates this.
Menu 21.1.3 - Filter Rules Summary
# A Type Filter Rules M m n
- - ---- --------------------------------------------------------- - - -
1 Y IP Pr=6, SA=0.0.0.0, DA=0.0.0.0, DP=23 N D F
2 N
3 N
4 N
5 N
6 N
Enter Filter Rule Number (1-6) to Configure:
# A Type Filter Rules M m n
- - ---- --------------------------------------------------------- - - -
1 Y IP Pr=6, SA=0.0.0.0, DA=0.0.0.0, DP=23 N D F
2 N
3 N
4 N
5 N
6 N
Enter Filter Rule Number (1-6) to Configure: