ZyXEL Communications P-793H User Manual

 Chapter 30 Filter Configuration

P-793H User’s Guide

For generic rules, the ZyXEL Device treats a packet as a byte stream as opposed to an IP or 
IPX packet. You specify the portion of the packet to check with the Offset (from 0) and the 
Length fields, both in bytes. The ZyXEL Device applies the Mask (bit-wise ANDing) to the 
data portion before comparing the result against the Value to determine a match. The Mask 
and Value are specified in hexadecimal numbers. Note that it takes two hexadecimal digits to 
represent a byte, so if the length is 4, the value in either field will take 8 digits, for example, 
FFFFFFFF.
To configure a generic rule, select Generic Filter Rule in the Filter Type field in menu 
21.1.1.1 and press [ENTER] to open Generic Filter Rule, as shown below.

Figure 193   Menu 21.1.1.1: Generic Filter Rule

The following table describes the fields in the Generic Filter Rule menu.

                         Menu 21.1.1.1 - Generic Filter Rule

                    Filter #: 1,1
                    Filter Type= Generic Filter Rule
                    Active= No
                    Offset= 0
                    Length= 0
                    Mask= N/A
                    Value= N/A
                    More= No           Log= None
                    Action Matched= Check Next Rule
                    Action Not Matched= Check Next Rule

Table 117   Menu 21.1.1.1: Generic Filter Rule

Filter #

This is the filter set, filter rule co-ordinates, in other words 2,3 refers to the second filter 

set and the third rule of that set.

Filter Type Use [SPACE BAR] and then [ENTER] to select a rule type. Parameters displayed below 

each type will be different. TCP/IP filter rules are used to filter IP packets while generic 

filter rules allow filtering of non-IP packets.
Options are Generic Filter Rule and TCP/IP Filter Rule.

Active

Select Yes to turn on the filter rule or No to turn it off.

Offset

Enter the starting byte of the data portion in the packet that you wish to compare. The 

range for this field is from 0 to 255.

Length

Enter the byte count of the data portion in the packet that you wish to compare. The range 

for this field is 0 to 8. 

Mask

Enter the mask (in Hexadecimal notation) to apply to the data portion before comparison.

Value

Enter the value (in Hexadecimal notation) to compare with the data portion.

More

If Yes, a matching packet is passed to the next filter rule before an action is taken; else 

the packet is disposed of according to the action fields.
If More is Yes, then Action Matched and Action Not Matched will be No.

Log

Select the logging option from the following:

None - No packets will be logged.

Action Matched - Only packets that match the rule parameters will be logged.

Action Not Matched - Only packets that do not match the rule parameters will be logged.

Both – All packets will be logged.