ZyXEL Communications Prestige 643 - Manual (Page 119)

Prestige 643 ADSL Router
Filter Configuration 8-19
Step 5. Enter 1 to configure the first filter rule. Make the entries in this menu as shown in next:
Figure 8-14 Example Filter – Menu 21.3.1
When you press [ENTER] to confirm, you will see the following screen. Note that there is only one filter
rule in this set.
Menu 21.3.1 - TCP/IP Filter Rule
Filter #: 3,1
Filter Type= TCP/IP Filter Rule
Active= Yes
IP Protocol= 6 IP Source Route= No
Destination: IP Addr= 0.0.0.0
IP Mask= 0.0.0.0
Port #= 23
Port # Comp= Equal
Source: IP Addr= 0.0.0.0
IP Mask= 0.0.0.0
Port #=
Port # Comp= None
TCP Estab= No
More= No Log= None
Action Matched= Drop
Action Not Matched= Forward
Press ENTER to Confirm or ESC to Cancel:
Press Space Bar to Toggle.
Press [SPACE BAR] to choose this filter rule
type. The first filter rule type determines all
subsequent filter types within a set.
Select Yes to make the rule active.
6 is the TCP protocol.
The port number for the telnet service
(TCP protocol) is 23. See RFC 1060 for
port numbers of well-known services.
Select Equal here as we are looking for
packets going to port 23 only.
There are no more
rules to check.
Select Drop here so that
the packet will be dropped
if its destination is the
telnet port.
Select Forward here so that the
packet will be forwarded if its
destination is not the telnet port.