As figure 7.4 demonstrates, Ethernet adapters that do not use/support VLAN tagging themselves, can still function without problems in an environment with VLANs, by having the switch (POWER Hypervisor) perform the tagging with the port VLAN ID of the virtual Ethernet adapter.
A virtual Ethernet adapter can optionally be created as IEEE 802.1q compatible (attribute ieee_virtual_eth=yes). In addition to untagged packets, it then also supports tagged packets for a list of VLAN IDs that can be specified with the attribute addl_vlan_ids. Then, several different VLANs can be used by one LPAR via a virtual Ethernet adapter. The virtual Ethernet adapter adds a VLAN header to the packets for the additional VLAN IDs. The packets therefore arrive at the virtual switch as tagged packets and the hypervisor no longer needs to add a VLAN tag.
Figure 7.5 shows the delivery of a packet with VLAN ID 200: VLAN ID 200 belongs to the additional VLAN IDs (addl_vlan_ids) of the sending virtual Ethernet adapter, so the virtual Ethernet adapter must generate a tagged packet. The packet is then forwarded unchanged to the virtual Ethernet switch. The VLAN ID 200 also belongs to the additional VLAN IDs for the target Ethernet adapter. The VLAN header is therefore not removed by the hypervisor and the packet including the VLAN header is forwarded to the target LPAR by the virtual Ethernet adapter. The VLAN header is retained during the entire delivery from the source LPAR to the destination LPAR!
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