Methods for performing power management of InfiniBand (IB) switches and apparatus and software configured to implement the methods. Power management datagrams (MADs) are used to inform IB switches that host servers connected to the IB switch's ports are to transition to a reduced-power or offline state or have returned to a normal operating state. A subnet management agent (SMA) on the IB switch receives the power MADs from the host servers and tracks each server's operating state. In response to power down MADs, the SMA coordinates power reduction of the switch's ports and other switch circuitry. For switches with multi-port IB interfaces, a multi-port interface is caused to enter a reduced-power state when all of its ports are connected to host servers that are idle or offline. Additionally, when all of a switch's ports are connected to idle or offline servers the SMA may put the switch's core switch logic into a reduced-power state. Power MADs are also used to inform upstream IB switches when a switch is to transition to a reduced power state or has returned to a normal operating state.