Systems and methods for providing multicast group (MCG) membership relative to partition membership in a high performance computing environment. In accordance with an embodiment, by allowing a subnet manager of a local subnet to be instructed that all ports that are members of the relevant partition should be set up as members for a specific multicast group, the SM can perform a more efficient multicast-routing process. It is also possible to limit the IB client interaction with subnet administration conventionally required to handle join and leave operations. Additionally, subnet manager overhead can be reduced by creating a spanning tree for the routing of multicast packets that includes each of the partition members added to the multicast group, instead of creating a spanning tree after each multicast group join request is received, as conventionally required.