Bay Technical Associates RM356 Chapter Filter Configuration, Outgoing Packet Filtering Process

Chapter 8

Filter Configuration

This chapter provides information about using filters and configuring filters for your Model RM356 Modem Router.

The router uses filters to decide whether to allow passage of a data packet and/or to make a call over the phone line. Three types of filters are involved: incoming data filters, outgoing data filters, and call filters. Data filters screen the data to determine if the packet should be allowed to pass. Call filters are used to determine if a call should be placed.

Outgoing packets must pass through the data filters before they encounter call filters. The call filters are divided into two groups: default call filters and user-defined call filters. The Model RM356 Modem Router has default call filters that filter out administrative packets (for example, RIP packets). The router applies the default filters first and then, if applicable, applies the user-defined call filters as shown in Figure 8-1.

Call filters

Outgoing

Data

No

match

	No
Built-in	match User-defined

No

match

Active data

Initiate call

packet

filters

Match

Drop

packet

default call		call filters
filters	(if applicable)
Match		Match
Drop packet		Drop packet
if line not up		if line not up

if line not up

Send packet

and reset idle timer

Figure 8-1.

Or	Or
Send packet	Send packet
but do not	but do not
reset idle timer	reset idle timer

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Outgoing Packet Filtering Process

Filter Configuration 8-1