ZyXEL Communications ZYWALL USG 20 - Firewall; Chapter 22 Firewall; Overview; What You Can Do in this Chapter

ZyWALL USG 20/20W User’s Guide
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CHAPTER 22
Firewall
22.1 Overview
Use the firewall to block or allow services that use static port numbers. The
firewall can also limit the number of user sessions.
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 225 Default Firewall Action
22.1.1 What You Can Do in this Chapter
•Use the Firewall screens (Section 22.2 on page 381) to enable or disable the
firewall and asymmetrical routes, and manage and configure firewall rules.
•Use the Session Limit screens (see Section 22.3 on page 386) to limit the
number of concurrent NAT/firewall sessions a client can use.