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Advanced POWER Virtualization on IBM System p5 - Previous ...

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Sending packets <strong>on</strong> a tagged or untagged port<br />

Before sending a packet out, the destinati<strong>on</strong> ports of the packet must be<br />

determined by the switch based <strong>on</strong> the destinati<strong>on</strong> MAC address in the packet.<br />

The destinati<strong>on</strong> port must have a PVID or VID matching the VLAN ID of the<br />

packet. If the packet is a broadcast (or multicast), it is forwarded to all (or many)<br />

ports in the VLAN, even using uplinks to other switches. If no valid destinati<strong>on</strong><br />

port can be determined, the packet is simply discarded. Finally, after internally<br />

forwarding the packet to the destinati<strong>on</strong> switch ports, before sending the packet<br />

out to the receiving host, the VLAN ID may be stripped-off or not, depending <strong>on</strong><br />

the port-type:<br />

► Tagged port sends out a packet:<br />

The PVID or VID remains tagged to the packet.<br />

► Untagged port sends out a packet:<br />

The PVID is stripped from the packet.<br />

Therefore, tagged and untagged switch ports behave similar with respect to<br />

receiving packets, but they behave different with respect to sending packets out.<br />

Ethernet adapters and interfaces in AIX 5L<br />

AIX 5L differentiates between a network adapter and network interface:<br />

Network adapter<br />

Network interface<br />

Represents the layer-2 device, for example, the Ethernet<br />

adapter ent0 has a MAC address, such as<br />

06:56:C0:00:20:03.<br />

Represents the layer-3 device, for example the Ethernet<br />

interface en0 has an IP address, such as 9.3.5.195.<br />

Typically, a network interface is attached to a network adapter, for example, an<br />

Ethernet interface en0 is attached to an Ethernet adapter ent0. There are also<br />

some network interfaces in AIX 5L that are not attached to a network adapter, for<br />

example, the loopback interface lo0 or a Virtual IP Address (VIPA) interface, such<br />

as vi0, if defined.<br />

Note: Linux does not distinguish between a network adapter and a network<br />

interface with respect to device naming: there is just <strong>on</strong>e device name for both.<br />

In Linux, a network device eth0 represents the network adapter and the<br />

network interface, and the device has attributes from layer-2 and layer-3, such<br />

as a MAC address and an IP address.<br />

When using VLAN, EtherChannel (EC), Link Aggregati<strong>on</strong>, (LA) or Network<br />

Interface Backup (NIB) with AIX 5L, the general c<strong>on</strong>cept is that Ethernet adapters<br />

are being associated with other Ethernet adapters, as shown in Figure 2-16 <strong>on</strong><br />

Chapter 2. <str<strong>on</strong>g>Virtualizati<strong>on</strong></str<strong>on</strong>g> technologies <strong>on</strong> <strong>System</strong> p servers 77

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