136 Chapter 11 Filter configurationNN47922-501Figure 61 Outgoing packet filtering processFor incoming packets, your Business Secure Router applies data filters only.Packets are processed depending upon whether a match is found. The followingsections describe how to configure filter sets.Filter StructureA filter set consists of one or more filter rules. Usually, you group related rules,for example, all the rules for NetBIOS, into a single set and give it a descriptivename. With the Business Secure Router, you can configure up to twelve filter setswith six rules in each set, for a total of 72 filter rules in the system. You cannotmix device filter rules and protocol filter rules within the same set. You can applyup to four filter sets to a particular port to block multiple types of packets. Witheach filter set having up to six rules, you can have a maximum of 24 rules activefor a single port.Sets of factory default filter rules are configured in menu 21 to prevent NetBIOStraffic from triggering calls and to prevent incoming Telnet sessions. A summaryof their filter rules is shown in the figures that follow.Figure 62 illustrates the logic flow when executing a filter rule. Also seeFigure 66 for the logic flow when executing an IP filter.DataFilteringOutgoingPacketDroppacketBuilt-indefaultCall FiltersUser-definedCall Filters(if applicable)Initiatecallif linenot upActiveDataSendpacketandresetIdleTimerOr OrDroppacketif linenot upDroppacketif linenot upSendpacketbut donot resetIdleTimerSendpacketbut donot resetIdleTimerMatch MatchMatchNomatchNomatchNomatchCall Filtering
