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Chapter 24 Firewall
ZyWALL USG 300 User’s Guide
450
24.1.2 What You Need to Know
Stateful Inspection
The ZyWALL has a stateful inspection firewall. The ZyWALL restricts access by
screening data packets against defined access rules. It also inspects sessions. For
example, traffic from one zone is not allowed unless it is initiated by a computer in
another zone first.
Zones
A zone is a group of interfaces or VPN tunnels. Group the ZyWALL’s interfaces into
different zones based on your needs. You can configure firewall rules for data
passing between zones or even between interfaces and/or VPN tunnels in a zone.
Default Firewall Behavior
Firewall rules are grouped based on the direction of travel of packets to which they
apply. Here is the default firewall behavior for traffic going through the ZyWALL in
various directions.
Table 116 Default Firewall Behavior
FROM ZONE TO ZONE BEHAVIOR
From WAN to ZyWALL Traffic from the WAN to the ZyWALL itself is allowed for certain
default services described in To-ZyWALL Rules on page 451. All
other WAN to ZyWALL traffic is dropped.
From WAN to any (other
than the ZyWALL)
Traffic from the WAN to any of the networks behind the
ZyWALL is dropped.
From DMZ to ZyWALL Traffic from the DMZ to the ZyWALL itself is allowed for certain
default services described in To-ZyWALL Rules on page 451. All
other DMZ to ZyWALL traffic is dropped.
From DMZ to any (other
than the ZyWALL)
Traffic from the DMZ to any of the networks behind the
ZyWALL is dropped.
From WLAN to WAN Traffic from the WLAN to the WAN is allowed.
From WLAN to ZyWALL Traffic from the WLAN to the ZyWALL itself is allowed for
certain default services described in To-ZyWALL Rules on page
451. All other WLAN to ZyWALL traffic is dropped.
From WLAN to any
(other than the ZyWALL)
Traffic from the WLAN to any of the networks behind the
ZyWALL is dropped.
From ANY to ANY Traffic that does not match any firewall rule is allowed. So for
example, LAN to WAN, LAN to DMZ, and LAN to WLAN traffic is
allowed. This also includes traffic to or from interfaces or VPN
tunnels that are not assigned to a zone (extra-zone traffic).