High Performance Two Port 10/100 Managed Ethernet Switch with
Datasheet
6.5.6Adding, Removing, and Changing VLAN Tags
Based on the port configuration and the received packet formation, a VLAN tag can be added to, removed from, or modified in a packet. There are four received packet type cases:
The
Dumb Port - This port type generally does not change the tag.
When a received packet is
When a packet is received
Access Port - This port type generally does not support tagging. When a received packet in
When a received packet is
When a received packet is
CPU Port - Packets transmitted from this port type generally contain a special tag. Special tags are described in detail in Section 6.4.10, "Host CPU Port Special Tagging," on page 75.
Hybrid Port - Generally, this port type supports a mix of
For clarity, the following details the incoming
When a received packet is
When a received packet is
If the
Otherwise, the tag is modified. The VID of the new VLAN tag is changed to the ingress ports default VID. If the Change Priority bit in the Buffer Manager Egress Port Type Register (BM_EGRSS_PORT_TYPE) for the egress port is set, then the Priority field of the new VLAN tag is also changed to the ingress ports default priority.
When a received packet is
If the
Else, if the Change Tag bit in the Buffer Manager Egress Port Type Register (BM_EGRSS_PORT_TYPE) for the egress port is clear, the packet is untouched.
Else, if both the Change VLAN ID and the Change Priority bits in the Buffer Manager Egress Port Type Register (BM_EGRSS_PORT_TYPE) for the egress port are clear, the packet passes untouched.
Otherwise, the tag is modified. If the Change VLAN ID bit for the egress port is set, the VOD of the new VLAN tag is changed to the egress ports default ID. If the Change Priority bit for the egress port is set, the Priority field of the new VLAN is changed to the egress ports default priority.
When a packet is received
SMSC LAN9312 | 79 | Revision 1.4 |
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