Cabletron Systems FRM, User Manual

Page: 218 / 396

14-4 Frame Relay Module 4. 0 User G uide, Rev 01
Figure 14-2 IPX SAP Filter Record
[A], [A],[E], [F],[B] from Main Menu
How Filter Masks Work
Each IPX filter parameter except
Filter Name
and
Server Name
is assigned a value and
an associated mask. 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 IPX packet as deter-
mined by
IPX 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
I PX Filter Definition s
* Filter Category 1–S AP
* Filter ID 1
A Filter Name filter_zxy
B Service Type V alu e 0004
C Service Type Mask 000f
D Server N ame s erver_123
E Network Add ress Value ff00ac00
F Network Add ress Mask ffff0000
G Node Add ress Value 10ac45000001
H Node Add ress Mask ffffff000000
I Socket A ddress Value 4000
J Socket A ddress Mas k f000
Option: