When you configure an IPMP group, the IPMP interface inherits the IP addresses of its underlying interfaces to use them as data addresses. The underlying interfaces then receive the IP address 0.0.0.0. Consequently, routes that are defined by using specific IP interfaces become lost if these interfaces are subsequently added to an IPMP group.
Loss of routing when configuring IPMP commonly involves the default route and occurs in association with an Oracle Solaris installation. During installation, you are required to define a default route, for which you use an interface that is on the system, such as the primary interface. Subsequently, you configure an IPMP group by using the same interface on which you defined the default route. After the IPMP configuration, the system can no longer route network packets because the interface's address was transferred to the IPMP interface.
To ensure that the default route is preserved while using IPMP, the route must be defined without specifying the interface. In this manner, any interface, including the IPMP interface, can be used for routing. Thus, the system can continue to route traffic.