ZyXEL Communications P-202 manual 2 TCP/IP Filter Rule, Protocol and Device Filter Sets

Prestige 201 ISDN Access Router

There are two categories of filter rules, Device Filter (Generic) rules and Protocol Filter (TCP/IP) rules. Device Filter rules act on the raw data from/to LAN and WAN. Protocol Filter rules act on the IP and IPX packets. Generic and TCP/IP filter rules are discussed in more detail in the next section. When NAT/SUA (Network Address Translation/Single User Account) is enabled, the inside IP address and port number are replaced on a connection-by-connection basis, which makes it impossible to know the exact address and port on the wire. Therefore, the Prestige applies the protocol filters to the “native” IP address and port number before NAT/SUA for outgoing packets and after NAT/SUA for incoming packets. On the other hand, the generic, or device filters are applied to the raw packets that appear on the wire. They are applied at the point when the Prestige is receiving and sending the packets; i.e. the interface. The interface can be Ethernet, or any other hardware port. The following diagram illustrates this.

Incoming

Device

Filters

Outgoing

Device

Filters

S U A

S U A

Incoming

Protocol

Filters

Outgoing

Protocol

Filters

Route

Figure 6-6 Protocol and Device Filter Sets

To speed up filtering, all rules in a filter set must be of the same class, i.e., protocol filters or generic filters. The class of a filter set is determined by the first rule that you create. When applying the filter sets to a port, separate menu fields are provided for protocol and device filter sets. If you include a protocol filter set in a device filters field or vice versa, the Prestige will warn you and will not allow you to save.

6.3.2 TCP/IP Filter Rule

This section shows you how to configure a TCP/IP filter rule. TCP/IP rules allow you to base the rule on the fields in the IP and the upper layer protocol, e.g., UDP and TCP, headers.

To configure a TCP/IP rules, select TCP/IP Filter Rule from the Filter Type field and press [Enter] to open Menu 21.1.1 - TCP/IP Filter Rule, as shown next.

6-8 Filter Configuration