When You Must Use IPMP

The configuration of an IPMP group is determined by your system configurations. Observe the following rules:

• Multiple IP interfaces on the same local area network or LAN must be configured into an IPMP group. LAN broadly refers to a variety of local network configurations including VLANs and both wired and wireless local networks whose nodes belong to the same link-layer broadcast domain.

• Underlying IP interfaces of an IPMP group must not span different LANs.

For example, suppose that a system with three interfaces is connected to two separate LANs. Two IP interfaces link to one LAN while a single IP interface connects to the other. In this case, the two IP interfaces connecting to the first LAN must be configured as an IPMP group, as required by the first rule. In compliance with the second rule, the single IP interface that connects to the second LAN cannot become a member of that IPMP group. No IPMP configuration is required of the single IP interface. However, you can configure the single interface into an IPMP group to monitor the interface's availability. The single-interface IPMP configuration is discussed further in Types of IPMP Interface Configurations.

Consider another case where the link to the first LAN consists of three IP interfaces while the other link consists of two interfaces. This setup requires the configuration of two IPMP groups: a three-interface group that links to the first LAN, and a two-interface group to connect to the second.