ZyXEL ZyWALL 5 User Guide - Page 703

Offset, Length, Value, Filter Type, Generic Filter Rule

Page 703 highlights

Chapter 46 Filter Configuration For generic rules, the ZyWALL 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 ZyWALL 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.x.x and press [ENTER] to open Generic Filter Rule, as shown below. Figure 442 Menu 21.1.1.1: Generic Filter Rule 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 Press ENTER to Confirm or ESC to Cancel: The following table describes the fields in the Generic Filter Rule menu. Table 249 Generic Filter Rule Menu Fields FIELD DESCRIPTION Filter # This is the filter set, filter rule co-ordinates, i.e., 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. ZyWALL 5/35/70 Series User's Guide 703

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Chapter 46 Filter Configuration
ZyWALL 5/35/70 Series User’s Guide
703
For generic rules, the ZyWALL 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 ZyWALL 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.x.x and press
[ENTER]
to open Generic Filter Rule, as shown below.
Figure 442
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
Press ENTER to Confirm or ESC to Cancel:
Table 249
Generic Filter Rule Menu Fields
FIELD
DESCRIPTION
Filter #
This is the filter set, filter rule co-ordinates, i.e., 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
.