An IPMP configuration typically consists of two or more physical interfaces on the same system that are attached to the same LAN. These interfaces can belong to an IPMP group in either of the following configurations:
active-active configuration – an IPMP group in which all underlying interfaces are active. An active interface is an IP interface that is currently available for use by the IPMP group. By default, an underlying interface becomes active when you configure the interface to become part of an IPMP group. For additional information about active interfaces and other IPMP terms, see also IPMP Terminology and Concepts.
active-standby configuration – an IPMP group in which at least one interface is administratively configured as a reserve. The reserve interface is called the standby interface. Although idle, the standby IP interface is monitored by the multipathing daemon to track the interface's availability, depending on how the interface is configured. If link-failure notification is supported by the interface, link-based failure detection is used. If the interface is configured with a test address, probe-based failure detection is also used. If an active interface fails, the standby interface is automatically deployed as needed. You can configure as many standby interfaces as you want for an IPMP group.
A single interface can also be configured in its own IPMP group. The single interface IPMP group has the same behavior as an IPMP group with multiple interfaces. However, this IPMP configuration does not provide high availability for network traffic. If the underlying interface fails, then the system loses all capability to send or receive traffic. The purpose of configuring a single-interfaced IPMP group is to monitor the availability of the interface by using failure detection. By configuring a test address on the interface, you can set the daemon to track the interface by using probe-based failure detection. Typically, a single-interfaced IPMP group configuration is used in conjunction with other technologies that have broader failover capabilities, such as Sun Cluster software. The system can continue to monitor the status of the underlying interface. But the Sun Cluster software provides the functionalities to ensure availability of the network when failure occurs. For more information about the Sun Cluster software, see Sun Cluster Overview for Solaris OS.
An IPMP group without underlying interfaces can also exist, such as a group whose underlying interfaces have been removed. The IPMP group is not destroyed, but the group cannot be used to send and receive traffic. As underlying IP interfaces are brought online for the group, then the data addresses of the IPMP interface are allocated to these interfaces and the system resumes hosting network traffic.