3Com corebuilder 3500 Implementation Manual page 227

The Ethernet and FDDI packet fields in Figure 35 are used as operands in
the packet filter. The two simplest operands are described in Table 32.
Table 32 Two Packet Filter Operands
Operand Description
packet field A field in the packet that can reside at any offset.
The size of the field can be 1, 2, 4, or 6 bytes.
Typically, you only specify a 6-byte field when you
want the filter to examine a 48-bit address.
constant A literal value to which you are comparing a packet
field. As with a field, a constant can be 1, 2, 4, or 6
bytes long.
The Packet Filtering Language
Opcode
pushField
pushLiteral
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