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10/100 Mbps Ethernet Controller Family Open Source Software Developer Manual 147
Wake-up Functionality
— Pre-Defined Filters.
The 82559 contains pre-defined filters for both Ethernet Type II and 802.2 snap. The
82559 distinguishes between these two types according to the MAC Type/Length field.
The 82559 also handles VLAN tagging per packet filter as described below. The Magic
Packet filter is a unique pre-defined filter, enabled by the configuration command. All
other pre-defined filters are controlled by the load programmable filter command.
Filter Type:
Filter Type Reserved (0) Word Match
31 30 29 28 27 26 25 24
EL FIX=1 VLAN NBH ARP IA-Type IA-Match TCO
EL The EL bit indicates if this filter is the last active one.
FIX If this bit is set 1, it indicates a pre-defined filter.
VLAN
When this bit is active (1), the 82559 skips a 4-byte field of the VLAN type tagging (byte
offsets 12 through 15). The VLAN bit affects only the filters defined in the same byte.
Other filters that may possibly be affected are the ARP and IA-Type filters.
NBH
The neighborhood filter looks for a word match defining a 2-byte field within the MAC
destination address to be compared. These two bytes compose a hash value of the
node IP address located in offset 02h and 03h of the MAC address. The active fields of
the NBH filter are shown below:
Byte Offset
0
3, 2
Pattern
Odd value
Word match
Meaning
LSB of the MAC destination address.
Hash value of the destination IP address.
ARP
The ARP filter is used to find a word match with the lower 16 bits of the IP address.
Typically, it is ideal for IP filtering. ARP filtering is based on the active fields shown
below. The byte offset of the active fields in 802.2 snap type are shifted by 8 bytes
ahead. If the filter VLAN flag is set, it is shifted by 4 bytes. For example, the opcode byte
is at offset 21 in EII with no VLAN and at offset 33 in 802.2 snap with active VLAN.