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

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2.8.2 Inter-partiti<strong>on</strong> networking with virtual Ethernet<br />

The <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor firmware implements a IEEE 802.1Q VLAN style virtual<br />

Ethernet switch. Similar to a physical IEEE 802.1Q Ethernet switch it can support<br />

tagged and untagged ports. Because a virtual switch, does not really need ports,<br />

the virtual ports corresp<strong>on</strong>d directly to virtual Ethernet adapters that can be<br />

assigned to LPARs from the HMC or IVM. There is no need to explicitly attach a<br />

virtual Ethernet adapter to a virtual Ethernet switch port. But to draw <strong>on</strong> the<br />

analogy of physical Ethernet switches, a virtual Ethernet switch port is c<strong>on</strong>figured<br />

when you c<strong>on</strong>figure the virtual Ethernet adapter <strong>on</strong> the HMC or IVM.<br />

For AIX 5L, a virtual Ethernet adapter is not much different from a real Ethernet<br />

adapter. It can be used:<br />

► To c<strong>on</strong>figure an Ethernet interface with an IP address <strong>on</strong>to it<br />

► To c<strong>on</strong>figure VLAN adapters (<strong>on</strong>e per VID) <strong>on</strong>to it<br />

► As a member of a Network Interface Backup adapter<br />

But it cannot be used for EtherChannel or Link Aggregati<strong>on</strong><br />

The <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor’s virtual Ethernet switch can support virtual Ethernet<br />

frames of up to 65408 bytes size, which is much larger than what physical<br />

switches support: 1522 bytes is standard and 9000 bytes are supported with<br />

Gigabit Ethernet Jumbo Frames. Thus, with the <str<strong>on</strong>g>POWER</str<strong>on</strong>g> Hypervisor’s virtual<br />

Ethernet, you can increase TCP/IP’s MTU size to 65394 (= 65408 - 14 for the<br />

header, no CRC) in the n<strong>on</strong>-VLAN-case and to 65390 (= 65408 - 14 - 4 for the<br />

VLAN, again no CRC) if you use VLAN. Increasing the MTU size is good for<br />

performance because it reduces processing due to headers and reduces the<br />

number of interrupts that the device driver has to react <strong>on</strong>.<br />

2.8.3 Sharing physical Ethernet adapters<br />

There are two approaches to c<strong>on</strong>nect a virtual Ethernet, that enables<br />

inter-partiti<strong>on</strong> communicati<strong>on</strong> <strong>on</strong> the same server, to an external network:<br />

Routing<br />

Layer-3 IP packet forwarding<br />

Bridging<br />

Layer-2 Ethernet frame forwarding<br />

Routing<br />

By enabling the IP forwarding capabilities of an AIX 5L or Linux partiti<strong>on</strong> with<br />

virtual and physical Ethernet adapters, the partiti<strong>on</strong> can act as router.<br />

Figure 2-17 <strong>on</strong> page 80 shows a sample c<strong>on</strong>figurati<strong>on</strong>. The client partiti<strong>on</strong>s<br />

would have their default routes set to the partiti<strong>on</strong>, which routes the traffic to the<br />

external network.<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 79

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