We specified a mechanism with which Mobile IPv6 and IPsec/IKE can work together efficiently. The interaction is necessary for updating the endpoint address of an IPsec tunnel in accordance with movement performed by a mobile node. Based on an analysis of needs for interaction between Mobile IPv6 and IPsec/IKE, we designed and implemented a mechanism that is an extension to the PF_KEY framework. The proposed mechanism allows Mobile IPv6 to inform IPsec/IKE of the movement so that necessary updates to the security policy database and security association database can be taken by IPsec/IKE.This notification helps IKE to update its internal state. The mechanism is also applicable to the other scenarios, such as NEMO, Mobile VPN and its variants.