TP-Link TL-SL5428E User Manual page 84

 MAC address duplication: After port configuration synchronization, packets from Secondary
VLAN can be forwarded via the promiscuous port untagged, and those from Primary VLAN
can be sent via the host port untagged. In order for these packets can be forwarded in
unicast via the right port, MAC address duplication is used to expand the VLANs the MAC
address is in. Normally, the egress ports for forwarding these packets are identified through
MAC address learning. For example the switch in Figure 6-16 maintains a MAC address
table shown in Table 6-6. The MAC address duplication process has two aspects, that is,
duplicating the dynamic MAC addresses learned by the host ports in the secondary VLANs
to the Primary VLAN and copying the dynamic MAC addresses learned by the promiscuous
ports in the Primary VLAN to the secondary VLANs. As shown in Figure 6-16, supposing
the Router sends a packet with the source MAC as mac_2 and the destination Mac as
mac_a. The MAC address table on the switch is changed to the one shown in Table 6-7.
Destination MAC
Destination MAC
mac_a
mac_a
mac_a
mac_2
mac_2
mac_3
mac_3
 Packet forwarding in Private VLAN
VLAN
mac_a
mac_2
mac_3
Table 6-6 MAC address table before duplication
VLAN
Table 6-7 MAC address table after duplication
Egress Port
5
2
3
Egress Port
5
2
3
2
5
3
5
75
port 5
port 2
port 3
port 5
port 5
port 5
port 2
port 2
port 3
port 3