Enterasys 6000 用户指南
Configuring Bridging
13-7
How Filter Masks Work
Most Bridge filter parameters are assigned values and associated "masks." The mask
determines (by the process described below) whether the filter will be applied to the
packet.
determines (by the process described below) whether the filter will be applied to the
packet.
The binary bits of the mask will be "ANDed" (0+0=0, 0+1=0, 1+1=1) to the value, as
in this example:
in this example:
Assume the value (hex) is
1234
and the mask is
5678
. The binary "ANDing" is as
follows:
Value:
0001001000110100
Mask:
0101011001111000
AND Result:
0001001000110000
The mask will also be ANDed to its corresponding field in each Bridged packet as
determined by Bridge Filter Applications (described later in this chapter). This result
will be compared to the AND result of the configured value and mask. If the two
results match, the filter will be applied. This process allows a number of packet field
values to match the AND result of the mask and value; for example:
determined by Bridge Filter Applications (described later in this chapter). This result
will be compared to the AND result of the configured value and mask. If the two
results match, the filter will be applied. This process allows a number of packet field
values to match the AND result of the mask and value; for example:
Packet field =
1233
, Mask =
5678
:Packet field =
1237
, Mask =
5678
:
Binary value:
0001001000110011
Value:
0001001000110111
Mask:
0101011001111000
Mask:
0101011001111000
AND Result:
0001001000110000
AND Result:
0001001000110000
Bridge Filter Parameters
Table 13-2 through Table 13-6 list the various filter parameters. Explanations of some
parameters follow the tables. Explanations of individual masks are not included below
because they were described in general under "How Filter Masks Work" on page 13-7.
parameters follow the tables. Explanations of individual masks are not included below
because they were described in general under "How Filter Masks Work" on page 13-7.
Table 13-2 Bridge Generic Filter Parameters
Parameter
Valid Values
Default Value
Fi lter Name
1–31 characters
none
Sq
1–16
1
Offset
0–254
(octets)
0
Value
0–ff
(hex)
0
Mask
0–ff
(hex)
0
Del
Allows you to delete the specific entry (defined by the sequence number)