Figure 91 Security > Firewall > Default Rule (Router Mode); Table 39 Security > Firewall > Default Rule (Router Mode) - ZyXEL Communications ZYWALL P1 User Manual

Figure 91 SECURITY > FIREWALL > Default Rule (Router Mode)
The following table describes the labels in this screen.
Table 39 SECURITY > FIREWALL > Default Rule (Router Mode)
LABEL
Enable Firewall
Allow
Asymmetrical
Route
ZyWALL P1 User's Guide
DESCRIPTION
Select this check box to activate the firewall. The ZyWALL performs access control
and protects against Denial of Service (DoS) attacks when the firewall is activated.
If an alternate gateway on the LAN has an IP address in the same subnet as the
ZyWALL's LAN IP address, return traffic may not go through the ZyWALL. This is
called an asymmetrical or "triangle" route. This causes the ZyWALL to reset the
connection, as the connection has not been acknowledged.
Select this check box to have the ZyWALL permit the use of asymmetrical route
topology on the network (not reset the connection).
Note: Allowing asymmetrical routes may let traffic from the WAN go
directly to the LAN without passing through the ZyWALL. A
better solution is to use IP alias to put the ZyWALL and the
backup gateway on separate subnets. See
page 150 for an example.
Chapter 9 Firewall
Section 9.6.1 on
151