There are a few common scenarios for using link aggregation.
Computer to computer
In this scenario, you connect the servers directly using the physical links of the link aggregate.
This allows the two servers to communicate at a higher speed without the need for a switch. This configuration is ideal for ensuring back-end redundancy.
Computer to switch
In this scenario, you connect your server to a switch configured for 802.3ad link aggregation.
The switch should have bandwidth for handling incoming traffic equal to or greater than that of the link aggregate (logical link) you define on your server.
For example, if you create an aggregate of four 1-Gbit/s links, use a switch that can handle incoming traffic (from clients) at 4 Gbit/s or more. Otherwise, the increased bandwidth advantage in the link aggregate won’t be fully realized.
Note: For information about how to configure your switch for 802.3ad link aggregation, see the documentation provided by the switch manufacturer.
Computer to switch-pair
In this scenario, you improve on the computer-to-switch scenario by using two switches to eliminate the switch as a single point of failure.
For example, you can connect two links to the master switch and the remaining links to the backup switch. As long as the master switch is active, the backup switch remains inactive. If the master switch fails, the backup switch takes over transparently.
Although this scenario adds redundancy that protects the server from becoming unavailable if the switch fails, it results in decreased bandwidth.