Disclosed here is a communication apparatus and method for inter-AS routing, which enables policy routing between a stub AS and an upstream AS. The policy routing includes control which is applicable only between adjacent autonomous systems (AS's). When a subject communication apparatus notifies its own AS number or advertises attribute information that includes its own AS number to a stub AS, the communication apparatus does not use its own AS number or uses the AS number of the upstream autonomous system (AS) instead of its own AS number. In addition, when relaying routing information received from one AS to another, the subject communication apparatus also relays attribute information without discarding the information, although the information is conventionally not relayed to itself.