ZyXEL Communications NBG-4600N User Manual page 184

Chapter 13 Firewall
Table 63 Security > Firewall > Services
LABEL
Do not respond
to requests for
unauthorized
services
Firewall Rule
#
Active
Service Name
IP
Schedule
Log
Modify
Add
Move
Misc setting
Bypass Triangle
Route
Max NAT/
Firewall Session
Per User
Apply
Reset
184
DESCRIPTION
Select this option to prevent hackers from finding the NBG-460N by
probing for unused ports. If you select this option, the NBG-460N will
not respond to port request(s) for unused ports, thus leaving the
unused ports and the NBG-460N unseen. By default this option is not
selected and the NBG-460N will reply with an ICMP Port Unreachable
packet for a port probe on its unused UDP ports, and a TCP Reset
packet for a port probe on its unused TCP ports.
Note that the probing packets must first traverse the NBG-460N's
firewall mechanism before reaching this anti-probing mechanism.
Therefore if the firewall mechanism blocks a probing packet, the NBG-
460N reacts based on the firewall policy, which by default, is to send a
TCP reset packet for a blocked TCP packet. You can use the command
"sys firewall tcprst rst [on|off]" to change this policy. When the firewall
mechanism blocks a UDP packet, it drops the packet without sending a
response packet.
This is your firewall rule number. The ordering of your rules is important
as rules are applied in turn. Use the Move button to rearrange the
order of the rules.
This icon is green when the rule is turned on. The icon is grey when the
rule is turned off.
This field displays the services and port numbers to which this firewall
rule applies.
This field displays the IP address(es) the rule applies to.
This field displays the days the firewall rule is active.
This field shows you whether a log will be created when packets match
the rule (Match) or not (No).
Click the Edit icon to modify an existing rule setting in the fields under
the Add Firewall Rule screen.
Click the Remove icon to delete a rule. Note that subsequent firewall
rules move up by one when you take this action.
Click the Add button to display the screen where you can configure a
new firewall rule. Modify the number in the textbox to add the rule
before a specific rule number.
The Move button moves a rule to a different position. In the first text
box enter the number of the rule you wish to move. In the second text
box enter the number of the rule you wish to move the first rule to and
click the Move button.
Select this check box to have the NBG-460N firewall ignore the use of
triangle route topology on the network.
Type a number ranging from 1 to 16000 to limit the number of NAT/
firewall sessions that a host can create.
Click Apply to save the settings.
Click Reset to start configuring this screen again.
NBG-460N User's Guide