When a communication apparatus receives a packet in accordance with a predetermined protocol through a second connection IF different from a first connection IF to which a packet having a same address as an address included in the packet in accordance with the predetermined preset protocol has so far been connected, a management unit receives a notification from the communication apparatus, and checks, with reference to a storage storing information on one or more connection Ifs supporting address floating, whether or not the first connection IF and the second connection IF of the communication apparatus belong to a common connection IF group that supports address floating to determine presence or absence of the address floating.