Filtering on Vendor Code in the Destination Address:
The first three bytes of the
station address are consistent for a given vendor. For all Hewlett-Packard devices, for example,
the first three bytes are 080009 (in hexadecimal).
The destination address is the first field that is analyzed by the bridge in IEEE 802.3 and
Ethernet packets, so the byte offset is 0. (The bridge strips off the Preamble and Start Frame
Delimiter fields.)
To use the vendor code in the destination address field to discard packets going to
Hewlett-Packard devices, the wildcard filter to enter is:
0000-1000-0000-0000-0000-1001-XXX X-XX XX 0
Note that only the first 24 of the wildcard filter’s 32 bits are needed to match the vendor code,
but all 32 bits must be specified. Xs are used for the last 8 bits since a specific match in those
bit positions is not needed.
Filtering on Vendor Code in the Source Address:
The source address is the second
field in IEEE 802.3 and Ethernet packets, so the byte offset is 6 (the first field is 6 bytes long).
To use the vendor code in the source address field to discard packets from Hewlett-Packard
devices, the wildcard filter to enter is:
0000-1000-0000-0000-0000-1001-XXX X-XX XX 6
Filtering on Ethernet “Packet Type”:
In Ethernet packets, the third field is a 4-digit
hexadecimal number that is used to identify the packet as a specific type. The byte offset for
this field is 12. See appendix E, “Ethernet Packet Types”, for a list of types.
To discard packets that have a packet type of B47D, for example, the wildcard filter would be:
1011-0100-0111-1101-XX XX-X XXX -XXXX -XXX X 12
3-10 Configuration
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