Compatible Systems 5.4 manual AppleTalk Filtering 213, Get Zone List, Routing Filters Rtmp

Chapter 13 - AppleTalk Filtering 213

all packets. For NBP request and reply packets the NBPName, NBPType and NBPZone rules are also used. All other rules are ignored.

Get Zone List

The get-zone-list interpreter allows the filtering of outgoing get-zone-list replies on an interface. These replies contain the zone list displayed by the Chooser on a Macintosh when it is opened. Thus, the get-zone-list interpreter allows control of the zones that are seen on a Macintosh behind a device. The only rules used in this interpreter are the network, net-rangeand zone rules. All other rules are ignored.

Routing Filters (RTMP)

The RTMP interpreter allows network numbers in input and output Apple- Talk RTMP routing packets to be filtered on an interface. The only rules used in this interpreter are the network and net-rangerules. All other rules are ignored.

Basic AppleTalk Filter Rules and Syntax

At a minimum, every non-comment line in a filter set must include an action. However, an action alone will not create a useful filter rule (except for setting a default rule as noted above).

Every line in a packet filter set must begin with the actions permit, or deny, or the comment indicator #.

•Lines which begin with permit specify that a packet meeting the condi- tions should be passed by the filter.

•Lines which begin with deny specify that a packet meeting the condi- tions should be dropped by the filter.

•Lines which begin with # specify that the text on the line is a comment and should be ignored.

AppleTalk Filter Options

The basic action specified in the rule will almost always be accompanied with an option. AppleTalk filter options use some or all of a set of operators to determine whether the filter rule matches the information being examined or not. These operators are discussed below:

•eq, ==, or = These are allowable ways of writing an “equality” operator which will match if the value in the packet/information is equal to the value specified in the option expression.

•lt or < These are allowable ways of writing a “less than” operator which will match the packet/information if its value is less than the value spec- ified in the option expression.