Filter Types And Nat - ZyXEL Communications ZyWALL 10 User Manual

ZyWALL 10 Internet Security Gateway
# A Type
- - ---- --------------------------------------------------------------- - - -
1 Y IP Pr=6, SA=0.0.0.0, DA=0.0.0.0, DP=23
2 N
3 N
4 N
5 N
6 N
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).
Figure 7-14 Example Filter Rules Summary - Menu 21.1.3
After you've created the filter set, you must apply it.
Step 1. Enter 11 from the main menu to go to Menu 11.
Step 2. Go to the Edit Filter Sets field, press the [SPACEBAR] to toggle Yes to No and press
[ENTER].
Step 3. This brings you to Menu 11.5. Apply the TELNET_WAN filter set (filter set 3) as shown in
Figure 7-17.
Step 4. Press [ENTER] to confirm after you enter the set numbers and to leave Menu 11.5.
7.4

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. 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
ZyWALL applies the protocol filters to the "native" IP address and port number before NAT for outgoing
7-16
Menu 21.1.3 - Filter Rules Summary
Filter Rules
Enter Filter Rule Number (1-6) to Configure: 1
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).
M m n
N D F
Filters