Intel Gigabit Ethernet Expansion Card Installation Instructions Manual page 21

Note: Your Ethernet controllers support failover, which provides
automatic redundancy for your Ethernet controllers. Without
failover, you can have only one Ethernet controller from the I/O
expansion card attached to each virtual LAN or subnet. With
failover, you can configure more than one Ethernet controller from
the I/O expansion card to attach to the same virtual LAN or
subnet. Either one of the integrated Ethernet controllers can be
configured as the primary Ethernet controller. If you have
configured the controllers for failover and the primary link fails, the
secondary controller takes over. When the primary link is restored,
the Ethernet traffic switches back to the primary Ethernet controller.
(See your operating-system device driver documentation for
information about configuring for failover.)
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I/O-module
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Type 8677 rear view
Chapter 2. Installing the I/O expansion card
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