Cabletron Systems 1800 - Manual (Page 259)

Configuring Bridging 16-7
Figure 16-2 Bridge MAC Filter Configuration Screen
[A],[A],[E], [F],[G] from Main Menu
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.
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 1234 and the mask is F000 . The binary "ANDing" is as
follows:
Value: 0001001000110100
Mask: 1111000000000000
AND Result: 0001000000000000
The mask will also be ANDed to its corresponding field in each Bridged packet as
determined by
Bridge Filter Applications . 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 = F000 : Packet field = 1237 , Mask = F000 :
Binary value: 0001001000110011 Value: 0001001000110111
Mask: 1111000000000000 Mask: 1111000000000000
AND Result: 0001000000000000 AND Result: 0001000000000000
Node N ame= node_xyz
Bridge Filter D efinitions
* Filter Category 5–MA C
* Filter ID 1
A Filter Name filter_abc
B Sou rce MAC Ad dres s Value ff00ac00
C Sou rce MAC Ad dres s Mas k ffff0000
D Destination MAC Add ress V alu e 10ac45000001
E Destination MAC Add ress Mask ffffff000000
Op tion ::