ZyXEL Communications 2 Plus User Manual

 Chapter 11 Firewall

ZyWALL 2 Plus User’s Guide

Figure 135   SECURITY > FIREWALL > Default Rule (Router Mode)

The following table describes the labels in this screen. 

Table 48   SECURITY > FIREWALL > Default Rule (Router Mode)

0-100%

This bar displays the percentage of the ZyWALL’s firewall rules storage space that 

is currently in use. When the storage space is almost full, you should consider 

deleting unnecessary firewall rules before adding more firewall rules.

Enable Firewall

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.

Note: When you activate the firewall, all current connections through 

the ZyWALL are dropped when you apply your changes.

Allow 

Asymmetrical 

Route

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 

 for an example.