The IP network multipathing or IPMP is a facility provided by Solaris to provide fault-tolerance and load spreading for network interface cards (NICs).
With IPMP, two or more NICs are dedicated for each network to which the host connects.
Each interface can be assigned a static "test" IP address, which is used to assess the operational state of the interface.
The IPMP load spreading feature increases the machine's bandwidth by spreading the outbound load between all the cards in the same IPMP group.
in.mpathd is the daemon in the Solaris OS responsible for IPMP functionality.