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Description:
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wildcardFilter OBJECT-TYPE
SYNTAX OCTET STRING (SIZE(6))
ACCESS read-write
STATUS obsolete
DESCRIPTION
"This object contains the binary value used to
filter frames. The data in the frame at the offset
specified by the Wildcard offsets is XOR'ed with
this object after AND'ing with the Wildcard Mask.
If zero result occurs, the packet is discarded
(filtered).
Suppose the user specifies the following values:
data: 11001010 10101010 10101010 10101010
mask: 11100000 00000000 00000000 00000000
filter: 11100000 00000000 00000000 00000000
AND'ing data with the mask gives:
11000000 00000000 00000000 00000000
XOR'ing that value with the filter gives:
00100000 00000000 00000000 00000000
The non-zero result indicates no match (don't
discard).
Another example:
data: 10011010 10101010 10101010 10101010
mask: 10010000 00000000 00000000 00000000
filter: 10010000 00000000 00000000 00000000
AND'ing data with the mask gives:
10010000 00000000 00000000 00000000
XOR'ing that value with the filter gives:
00000000 00000000 00000000 00000000
A zero result indicates a match, so we discard
(filter) the packet.
The filter AND'ed with the mask must equal the
filter. This is an example of a legal filter/mask
pair:
filter: 00010000 00000000 00000000 00000000
mask: 10010000 00000000 00000000 00000000
AND'ed: 00010000 00000000 00000000 00000000
(equals filter)
Another way of saying this: if a mask bit is zero,
the corresponding filter bit must be zero.
The following would be an illegal pair:
filter: 01110000 00000000 00000000 00000000
mask: 10010000 00000000 00000000 00000000
AND'ed: 00010000 00000000 00000000 00000000
( != filter)"
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