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

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4.1.2 Using Link Aggregati<strong>on</strong> or EtherChannel to external networks<br />

Link Aggregati<strong>on</strong> is a network port aggregati<strong>on</strong> technology that allows several<br />

Ethernet adapters to be aggregated together to form a single pseudo Ethernet<br />

adapter. This technology is often used to overcome the bandwidth restricti<strong>on</strong> of a<br />

single network adapter and avoid bottlenecks when sharing <strong>on</strong>e network adapter<br />

am<strong>on</strong>g many client partiti<strong>on</strong>s.<br />

The main benefit of a Link Aggregati<strong>on</strong> is that it has the network bandwidth of all<br />

of its adapters in a single network presence. If an adapter fails, the packets are<br />

automatically sent <strong>on</strong> the next available adapter without disrupti<strong>on</strong> to existing<br />

user c<strong>on</strong>necti<strong>on</strong>s. The adapter is automatically returned to service <strong>on</strong> the Link<br />

Aggregati<strong>on</strong> when it recovers. Thus, Link Aggregati<strong>on</strong> also provides some<br />

degree of increased availability. A link or adapter failure will lead to a<br />

performance degradati<strong>on</strong>, but not a disrupti<strong>on</strong>.<br />

But Link Aggregati<strong>on</strong> is not a complete high-availability networking soluti<strong>on</strong><br />

because all the aggregated links must c<strong>on</strong>nect to the same switch. This<br />

restricti<strong>on</strong> can be overcome with the use of a backup adapter: You can add a<br />

single additi<strong>on</strong>al link to the Link Aggregati<strong>on</strong>, which is c<strong>on</strong>nected to a different<br />

Ethernet switch with the same VLAN. This single link will <strong>on</strong>ly be used as a<br />

backup.<br />

As an example for Link Aggregati<strong>on</strong>, ent0 and ent1 can be aggregated to ent2.<br />

The system c<strong>on</strong>siders these aggregated adapters as <strong>on</strong>e adapter. Interface en2<br />

would then be c<strong>on</strong>figured with an IP address. Therefore, IP is c<strong>on</strong>figured as <strong>on</strong><br />

any other Ethernet adapter. In additi<strong>on</strong>, all adapters in the Link Aggregati<strong>on</strong> are<br />

given the same hardware (MAC) address, so they are treated by remote systems<br />

as though they were <strong>on</strong>e adapter.<br />

There are two variants of Link Aggregati<strong>on</strong> supported in AIX 5L:<br />

► Cisco EtherChannel (EC)<br />

► IEEE 802.3ad Link Aggregati<strong>on</strong> (LA)<br />

Chapter 4. Setting up virtual I/O: advanced 187

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