ZyXEL Communications Corporation VMG1312T10C Manuel D’Utilisation

 Chapter 14 Firewall

VMG1312-T10C User’s Guide

can be carried out through ICMPv6. Since ICMPv6 error messages are critical for establishing and 
maintaining communications, filtering policy focuses on ICMPv6 informational messages.

If an outside user attempts to probe an unsupported port on your Device, an ICMP response packet 
is automatically returned. This allows the outside user to know the Device exists. The Device 
supports anti-probing, which prevents the ICMP response packet from being sent. This keeps 
outsiders from discovering your Device when unsupported ports are probed. 

Internet Control Message Protocol (ICMP) is a message control and error-reporting protocol 
between a host server and a gateway to the Internet. ICMP uses Internet Protocol (IP) datagrams, 
but the messages are processed by the TCP/IP software and directly apparent to the application 
user. 

For DoS attacks, the Device uses thresholds to determine when to drop sessions that do not 
become fully established. These thresholds apply globally to all sessions. You can use the default 
threshold values, or you can change them to values more suitable to your security requirements.

Use this screen to select the firewall protection level on the Device. Click Security > Firewall > 
General to display the following screen.

Security > Firewall > General