ZyXEL Communications 200 Series User Manual

ZyWALL USG 100/200 Series User’s Guide

Use the firewall to block or allow services that use static port numbers. Use application patrol 
(see 

) to control services using flexible/dynamic port numbers.

This figure shows the ZyWALL’s default firewall rules in action and demonstrates how 
stateful inspection works. User 1 can initiate a Telnet session from within the LAN1 zone and 
responses to this request are allowed. However, other Telnet traffic initiated from the WAN or 
DMZ zone and destined for the LAN1 zone is blocked. Communications between the WAN 
and the DMZ zones are allowed. The firewall allows VPN traffic between any of the networks.

Figure 237   Default Firewall Action

 

• Use the Firewall screen (

) to enable or disable the firewall and 

asymmetrical routes, set a maximum number of sessions per host, and display the 
configured firewall rules. 

• Use the Firewall Edit screen (see 

) to edit or add a firewall 

rule.