How Filter Masks Work; Bridge Filter Parameters; Bridge Generic Filter Parameters - Cabletron Systems SmartSwitch 6000 User Manual

How Filter Masks Work

Bridge Filter Parameters

Configuring Bridging
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.
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:
Assume the value (hex) is
follows:
Value:
Mask:
AND Result:
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:
Packet field =
1233
Binary value:
0001001000110011
Mask:
0101011001111000
AND Result:
0001001000110000
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.
Table 13-2 Bridge Generic Filter Parameters
Parameter
Filter Name
Sq
Offset
Value
Mask
Del Allows you to delete the specific entry (defined by the sequence number)
and the mask is
1234
0001001000110100
0101011001111000
0001001000110000
, Mask = :Packet field =
5678
Value:
Mask:
AND Result:
Valid Values
1–31 characters
1–16
0–254
0–ff
0–ff
. The binary "ANDing" is as
5678
, Mask =
1237 5678
0001001000110111
0101011001111000
0001001000110000
Default Value
none
1
0
(octets)
(hex) 0
(hex) 0
:
13-7