ExpWave 240B Secure Outdoor Ethernet Radio Link
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
Start
Fetch Next
Filter Set
Yes
Next Filter Set
Available?
Filter Set
Fetch Next
Filter Rule
Yes
Next filter
NoRule 
No Available?
Packet into filter
Fetch First Filter Set
Fetch First Filter Rule
Active?
Yes
No
Drop Packet
Execute
Filter Rule
Check
Next
Rule
Forward
Drop
Accept Packet
Figure| Filter Setup |
