ZyXEL P-202H User Guide - Page 245
Offset, Length, Value, Filter Type
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P-202H Plus v2 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.x.x and press [ENTER] to open Generic Filter Rule, as shown below. Figure 145 Menu 21.1.4.1 Generic Filter Rule Menu 21.1.4.1 - Generic Filter Rule Filter #: 4,1 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 81 Menu 21.1.x.x Generic Filter Rule Menu Fields FIELD Filter # Filter Type Active Offset Length Mask Value DESCRIPTION OPTIONS 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. 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. Generic Filter Rule TCP/IP Filter Rule Select Yes to turn on the filter rule or No to turn it off. Yes / No Enter the starting byte of the data portion in the packet that you wish 0-255 to compare. The range for this field is from 0 to 255. Enter the byte count of the data portion in the packet that you wish 0-8 to compare. The range for this field is 0 to 8. Enter the mask (in Hexadecimal notation) to apply to the data portion before comparison. Enter the value (in Hexadecimal notation) to compare with the data portion. Chapter 25 Filter Configuration 244