A communication apparatus that is capable of preventing data erroneous transmission without disturbing communication with a networking device. The communication apparatus is connectable with a plurality of networks including at least a first network and a second network. A specifying unit specifies an IP address of the communication apparatus that is used in communication with an external apparatus on the first network. A determination unit determines an IP address of which a network part is different from a network part of the IP address specified by the specifying unit as an IP address that will be distributed to an external apparatus on the second network. A distribution unit distributes the IP address determined by the determination unit to the external apparatus on the second network.