ROUTE INFORMATION RETRIEVING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a route information retrieving circuit retrieving route information faster by minimizing the number of accessing times to a memory storing a routing table. SOLUTION: An IP(internal protocol) address (32bits) is separated (102 to 106) into three parts (the common part of a high order, the route information referring part of an intermediate order and the subnet mask part of a smallest size IP network of a low order) from user's information (VPI)(virtual path identifier). Then the common part of the high order is used for collating arithmetic (108) for judging whether a sent cell is effective or ineffective. In addition, the intermediate-order bit is used as the memory address of route reference (107) with user information to assign route information to an area designated by the address. Thereby route information is obtained by once access to a memory.