A communication apparatus is provided in a redundant communication system including a plurality of communication apparatuses having mutually-redundant configurations, and is configured so that its operating mode can be switched between a plurality of modes including an active mode and a standby mode. The communication apparatus includes a synchronization control unit configured to share client identification information with another communication apparatus included in the redundant communication system, and an address acquisition unit configured to acquire, in response to switching of the operating mode to the active mode, an IP address from a DHCP server by using the client identification information.