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Defining Static Filters
Defining generic filters
MAX 6000/3000 Network Configuration Guide 15-9
Specifying the offset to the bytes to be examined
The offset in a generic filter is a byte-offset from the start of a packet to the start of the data in
the packet to be tested. For example, with the following filter specification:
Input Filters
In Filter NN
Generic...
Offset=2
Length=8
Mask=0f:ff:ff:ff:00:00:00:f0:00:00:00:00
Value=07:fe:45:70:00:00:00:90:00:00:00:00
Compare=no
More=no
or comparable RADIUS filter definition:
Ascend-Data Filter="generic in drop 2 0fffffff000000f 07fe45700000009"
and the following packet contents:
2A 31 97 FE 45 70 12 22 33 99 B4 80 75
the first two byes in the packet (2A and 31) are ignored because of the two-byte offset.
Specifying the number of bytes to test
In a RADIUS profile, the length of the mask and value must be equal, and the system tests that
number of bytes in the packet, starting at the specified offset. In a local Filter profile, the Len
setting specifies the number of bytes to test in a packet, starting with the byte specified by the
Offset parameter. The Mask setting is assumed have the same number of octets as the data
specified by the Length parameter.
For example, with the following filter specification:
Input Filters
In Filter NN
Generic...
Offset=2
Length=8
Mask=0f:ff:ff:ff:00:00:00:f0:00:00:00:00
Value=07:fe:45:70:00:00:00:90:00:00:00:00
Compare=no
More=no
and the following packet contents:
2A 31 97 FE 45 70 12 22 33 99 B4 80 75
the filter test the value of bytes three (97) through ten (99).