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3.2.3 VLAN Group Mapping
The VLAN group mapping is the switch
’
s decision process to find a right VLAN group for the re-
ceived packet when it is not filtered by ingress rules. The group mapping depends on the VLAN mode
and the packet type. The following table lists the decision rules:
VLAN Mode
Packet Type
Mapping Method
802.1Q Tag Aware
Tagged & non-Null
Use packet
’
s VID to loop up VLAN group table
Matched - use the group matched
Unmatched - drop the packet
802.1Q Tag Aware
Null VID
Use ingress port
’
s default VLAN group directly
802.1Q Tag Aware
Untagged
Use ingress port
’
s default VLAN group directly
Port-based VLAN
Tagged
Use ingress port
’
s default VLAN group directly
Port-based VLAN
Untagged
Use ingress port
’
s default VLAN group directly
3.2.4 Packet Forwarding under VLAN
The forwarding is a switch
’
s process to forward the received packet to one or more egress ports. The
process uses the following information as forwarding decision:
•
The mapped VLAN group
’
s member ports : the port range for forwarding
•
The packet
’
s destination MAC address : for MAC address table loop up
•
The switch
’
s MAC address table : to find the associated input port for a learned MAC address
If the MAC address table lookup is matched and the associated port is the VLAN member port, the
packet is forwarded to the port (egress port). If the lookup is not matched, the switch will broadcast the
packet to all member ports.
3.2.5 Egress Tagging Rules
Egress Tagging rules are used to make change to the packet before it is transmitted out from an egress
port. Two egress tagging settings are provided for each port and are described as follows:
3.2.5.1 Egress Tag Rule (per port setting)
Four basic options are provided for egress tagging :
1. Tagging with PVID for all packets
Untagged packet : the packet is inserted with the associated ingress port
’
s PVID as tag VID
Tagged packet : the packet
’
s tag VID is replaced with ingress port
’
s PVID as new tag VID
2. Untagging for all packets
Untagged packet : the packet is not modified
Tagged packet : the packet
’
s tag VID is removed and becomes an untagged packet
Null VID packet : depending on Null VID Replacement setting in next section
3. PVID insertion for untagged packets only
Untagged packet : the packet is inserted with the associated ingress port
’
s PVID as tag VID
Tagged packet : the packet is not modified
4. No tag insertion and tag removal
The packet is not modified at all. No tag insertion or tag removal are performed for all packets.
