ZyXEL P-660HW-T1 v3 User Guide - Page 227
Firewall Versus Filters
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Chapter 12 Packet Filter receiving and sending the packets; that is the interface. The interface can be an Ethernet port or any other hardware port. The following diagram illustrates this. Figure 95 Protocol and Generic Filter Sets Route Protocol Filters NAT Generic Incoming Interface Filters Outgoing 12.3.2 Firewall Versus Filters Below are some comparisons between the ZyXEL Device's filtering and firewall functions. Packet Filtering • The router filters packets as they pass through the router's interface according to the filter rules you designed. • Packet filtering is a powerful tool, yet can be complex to configure and maintain, especially if you need a chain of rules to filter a service. • Packet filtering only checks the header portion of an IP packet. When To Use Filtering 1 To block/allow LAN packets by their MAC addresses. 2 To block/allow special IP packets which are neither TCP nor UDP, nor ICMP packets. 3 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. Filters cannot distinguish traffic originating from an inside host or an outside host by IP address. 4 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. P-660HW-Tx v3 Series User's Guide 227