Altera cyclone V Technical Reference page 1274

cv_5v4
2016.10.28
Table 17-23: Source Address Filtering
Frame
Type
Unicast
VLAN Filtering
The EMAC supports the two kinds of VLAN filtering:
• VLAN tag-based filtering
• VLAN hash filtering
VLAN Tag-Based Filtering
In the VLAN tag-based frame filtering, the MAC compares the VLAN tag of the received frame and
provides the VLAN frame status to the application. Based on the programmed mode, the MAC compares
the lower 12 bits or all 16 bits of the received VLAN tag to determine the perfect match. If VLAN tag
filtering is enabled, the MAC forwards the VLAN-tagged frames along with VLAN tag match status and
drops the VLAN frames that do not match. You can also enable the inverse matching for VLAN frames. In
addition, you can enable matching of SVLAN tagged frames along with the default Customer Virtual
Local Area Network (C-VLAN) tagged frames.
VLAN Hash Filtering with a 16-Bit Hash Table
The MAC provides VLAN hash filtering with a 16-bit hash table. The MAC also supports the inverse
matching of the VLAN frames. In inverse matching mode, when the VLAN tag of a frame matches the
perfect or hash filter, the packet should be dropped. If the VLAN perfect and VLAN hash match are
enabled, a frame is considered as matched if either the VLAN hash or the VLAN perfect filter matches.
When inverse match is set, a packet is forwarded only when both perfect and hash filters indicate
†
mismatch.
Layer 3 and Layer 4 Filters
Layer 3 filtering refers to source address and destination address filtering. Layer 4 filtering refers to source
port and destination port filtering. The frames are filtered in the following ways:
• Matched frames
• Unmatched frames
• Non-TCP or UDP IP frames
Ethernet Media Access Controller
Send Feedback
†
PR DAIF
1 X
0 0
0 1
0 0
0 1
†
†
†
†
†
DBF Source Address Filter Operation
X
0 Pass status on Perfect or Group filter match but
do not drop frames that fail.
0 Fail on Perfect or Group filter match but do not
1 Pass on Perfect or Group filter match and drop
1 Fail on Perfect or Group filter match and drop
†
VLAN Filtering
Pass all frames
drop frame
frames that fail
frames that fail
†
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