ZyXEL Communications P-660HW-Tx v3 User Manual page 220

Chapter 11 Packet Filter
• To block/allow both inbound (WAN to LAN) and outbound (LAN to WAN) traffic
between the specific inside host/network "A" and outside host/network "B". If
the filter blocks the traffic from A to B, it also blocks the traffic from B to A.
Generic filters cannot distinguish traffic originating from an inside host or an
outside host by IP address or subnets.
• To block/allow IP trace route.
Firewall
• The firewall inspects packet contents as well as their source and destination
addresses. Firewalls of this type employ an inspection module, applicable to all
protocols, that understands data in the packet is intended for other layers, from
the network layer (IP headers) up to the application layer.
• The firewall performs stateful inspection. It takes into account the state of
connections it handles so that, for example, a legitimate incoming packet can be
matched with the outbound request for that packet and allowed in. Conversely,
an incoming packet masquerading as a response to a non-existent outbound
request can be blocked.
• The firewall uses session filtering, i.e., smart rules, that enhance the filtering
process and control the network session rather than control individual packets in
a session.
• The firewall provides e-mail service to notify you of routine reports and when
alerts occur.
When To Use The Firewall
• To prevent DoS attacks and prevent hackers cracking your network.
• A range of source and destination IP addresses as well as port numbers can be
specified within one firewall rule making the firewall a better choice when
complex rules are required.
• To selectively block/allow inbound or outbound traffic between inside host/
networks and outside host/networks. Remember that filters cannot distinguish
traffic originating from an inside host or an outside host by IP address.
• The firewall performs better than filtering if you need to check many rules.
• Use the firewall if you need routine e-mail reports about your system or need to
be alerted when attacks occur.
• The firewall can block specific URL traffic that might occur in the future. The URL
can be saved in an Access Control List (ACL) database.
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P-660HW-Tx v3 User's Guide