To provide an inter-network connection device which can speedily inform a manager of the insufficient capacity of a memory storing route information.

In the inter-network connection device which has a route information table 14 storing route information on the memory and which does not store route information and abolishes it, if the number of stored route information exceeds the memory capacity that can be used, when route information is to be added to the route information table 14. A message information the lack of memory capacity is transmitted to the manager, when the number of abolished route information exceeds a threshold which has been set previously.