When you have only one network adapter in the multipathing group, you can configure the network adapter to detect failures on that NIC alone.
Although failovers cannot occur with only one NIC in the group, you still need a separate test address on each of the physical interfaces in the group. You can configure the test address as an IFF_NOFAILOVER address, which is sufficient for the daemon to send out probes on that interface. Unlike the multiple physical interface instance, you do not have to mark a single physical interface as deprecated.
Use the following syntax to configure the interface's IPv4 address as a NOFAILOVER:
# ifconfig interface-name -failover group group-name
For IPv6, use the following syntax:
# ifconfig interface-name inet6 -failover group group-name
When the daemon detects failures, the interface is marked and logged appropriately on the console.
You cannot verify whether the target that is being probed has failed or the NIC has failed, because the target can be probed through only one physical interface. If only one default router is on the subnet, turn off multipathing if a single physical interface is in the group. If a separate IPv4 and IPv6 default router exists (or multiple default routers exist), more than one target needs to be probed. Hence, you can safely turn on multipathing.