ZyXEL Communications NBG420N - Manual (Page 157)

Chapter 13 Firewall
NBG420N User’s Guide
157
13.4.1 The Add Firewall Rule Screen
If you click Add or the Modify icon on an existing rule, the Add Firewall Rule screen is
displayed. Use this screen to add a firewall rule or to modify an existing one.
Do not respond to
requests for
unauthorized
services
Select this option to prevent hackers from finding the NBG420N by probing for
unused ports. If you select this option, the NBG420N will not respond to port
request(s) for unused ports, thus leaving the unused ports and the NBG420N
unseen. By default this option is not selected and the NBG420N 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 NBG420N's firewall
mechanism before reaching this anti-probing mechanism. Therefore if the firewall
mechanism blocks a probing packet, the NBG420N 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.
Firewall Rule
# 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.
Active This icon is green when the rule is turned on. The icon is grey when the rule is
turned off.
Service Name This field displays the services and port numbers to which this firewall rule applies.
IP This field displays the IP address(es) the rule applies to.
Schedule This field displays the days the firewall rule is active.
Log This field shows you whether a log will be created when packets match the rule
(Match) or not (No).
Modify 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.
Add 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.
Move 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.
Misc setting
Bypass Triangle
Route
Select this check box to have the NBG420N firewall ignore the use of triangle
route topology on the network.
Max NAT/Firewall
Session Per User
Type a number ranging from 1 to 2048 to limit the number of NAT/firewall sessions
that a host can create.
Apply Click Apply to save the settings.
Reset Click Reset to start configuring this screen again.
Table 58 Security > Firewall > Services
LABEL DESCRIPTION