Figure 9-5 Protocol And Device Filter Sets; Filter Types And Sua - ZyXEL Communications Prestige 480 User Manual

Prestige 480 Dual BRI ISDN Router

9.3.1 Filter Types and SUA

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 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.
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.
Filter Configuration
Incoming
Device
Filters
Outgoing
Device
Filters

Figure 9-5 Protocol and Device Filter Sets

S
Incoming
U
Protocol
Filters
S
Outgoing
U Protocol
Filters
Route
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