A technique disclosed enables a node having a plurality of interfaces to conduct connection of the plurality of interfaces simultaneously in a communication network domain. A mobile node having a plurality of interfaces connects one of the interfaces with a MAG (mobile access gateway) 11a to take part in a NetLMM domain 18 using a NetLMM protocol, and a LMA (local mobility anchor) 13 includes association information with the MAG 11a registered therein. When the mobile node connects another interface with another MAG 11b, the LMA receives a registration request for association information of this mobile node with the MAG 11b, and makes an inquiry to the already registered MAG 11a as to whether link with the mobile node is still valid or not. If the link is valid, the LMA keeps association information of the mobile node with both of the MAGs 11a and 11b.