ZyXEL Communications ZyXEL ExpWave 240B - Manual (Page 55)

ExpWave 240B Secure Outdoor Ethernet Radio Link
Filter Setup 9-1
Chapter 9 Filter Setup Configuration
This chapter shows you how to create and apply filters.
9.1 About Filtering
Your ExpWave uses filters to decide whether to allow passage of a data packet and/or to make a call. There are two
types of filter applications: data filtering and call filtering. Filters are subdivided into device and protocol filters, which
are discussed later.
Data filtering screens the data to determine if the packet should be allowed to pass. Data filters are divided into
incoming and outgoing filters, depending on the direction of the packet relative to a port. Data filtering can be applied
on either the WAN side or the LAN side. For incoming packets, your ExpWave applies data filters. Packets are
processed depending upon whether a match is found. The following sections describe how to configure filter sets.
9.1.1 The Filter Structure of the ExpWave
A filter set consists of one or more filter rules. Usually, you would group related rules, e.g., all the rules for NetBIOS,
into a single set and give it a descriptive name. The ExpWave allows you to configure up to twelve filter sets with six
rules in each set, for a total of 72 filter rules in the system. You cannot mix device filter rules and protocol filter rules
within the same set. You can apply up to four filter sets to a particular port to block multiple types of packets. With
each filter set having up to six rules, you can have a maximum of 24 rules active for a single port. See Figure 9-1 Filter
Rule Process for the logic flow when executing an IP filter.
Start
Fetch First
Filter Set
Fetch First
Filter Rule
Active?
Execute
Filter Rule
Fetch Next
Filter Rule
Next filter
Rule
Available?
Fetch Next
Filter Set
Next Filter Set
Available?
Accept Packet Drop Packet
Yes
No
Yes
No
Yes
Packet into
filter
Filter Set
Forward
Drop
No
Check
Next
Rule
Figure 9-1 Filter Rule Process