LevelOne GEP-0950 - Manual (Page 35)

Port VLAN Identifier:
VLAN identifier of a port. It also can be referred to as PVID. When an
untagged frame or a priority-tagged frame is received, the frame will be inserted the
PVID of that port in the VLAN tag field. The frame with VID assigned by a port is
called PVID. Each port can only be assigned a PVID. The default value for PVID is
1, the same as VID.
Ingress filtering:
The process to check a received packet and compare its VID to the VLAN
membership of the ingress port. The ingress filtering can be set by per port. When
receiving a packet, VLAN bridge examines if the VID in the frame’s header presents.
If the VID of the received packet presents, the VID of the packet is used. And
VLAN bridge will check its MAC address table to see if the destination ports are
members of the same VLAN. If both are members of the tagged VLAN, then the
packet will be forwarded.
If the packet is an untagged or a null tag packet, the ingress port’s PVID is
applied to the packet. VLAN bridge will then look up the MAC address table and
determine to which ports the packet should be forwarded. Next, it will check to see if
the destination ports belong to the same VLAN with that PVID. If the destination
ports are members of the VLAN used by ingress port, the packet will be forwarded.
Note: VID can not be 0 or 4095.
Ingress Rule:
Each packet received by a VLAN-aware bridge will be classified to a VLAN.
The classification rule is described as follows.
1. If the VID of the packet is null VID (VID=0)or this packet is an untagged packet:
a. If there are still some other ways(e.g. protocol, MAC address, application,
IP-subnet, etc.) to classify the incoming packets beside port-based
classification in implement and these approaches can offer non-zero VID,
then, use the value of VID offered by other classifications for VLAN’s
classification.
b. If there is only port-based classification in implement or other classification
approaches cannot offer non-zero VID for the incoming packets, then
assign the PVID to the incoming packets as VID for the classification of
the VLAN group.
2. If the VID is not a null VID (VID≠0), then use the value to classify the VLAN group.
Egress Rule:
An egress list is used to make the tagging and forwarding decision on an
outgoing port. It specifies the VLANs whose packets can be transmitted out and
specifies if the packet should be tagged or not. It can be configured for port’s VLAN
membership, and tagged or untagged for a transmitted packet. When a packet is
transmitted out, the VLAN bridge checks the port’s egress list. If the VLAN of the
packet is on the egress list of the port on which the packet transmits out, the packet
will be transmitted with the priority accordingly. If enabled, an egress port will
transmit out a tagged packet if the port is connected to a 802.1Q-compliant device.
If an egress port is connected to a non-802.1Q device or an end station, VLAN
bridge must transmit out an untagged packet, i.e. the tag has been stripped off in an
egress port. Egress rule can be set by per port.