A method, system and device for protecting a network node by an access blocking function, such as a correspondent node firewall, are disclosed. The access blocking function protects either a first or a second network node and allows access to the protected network node from the other network node via a link associated to an address of the first network node and an address of the second network node. The second network node is configured to change its address. The method comprises associating the link associated to the old address of the second network node to the new address of the second network node when the second network node changes its address.