Abstract: A method to be carried out by an interface element (IE, 510) between a VNF pool (508) and a control entity (520) is disclosed. The VNF pool (508) comprises a plurality of VNF instances (502) including at least a first and second instances. The control entity (520) is configured to control the VNF instances (502) of the pool (508). The method enables the IE (510) to assist in replicating a state of the first VNF instance on the second VNF instance. The method includes steps of obtaining a control message provided from the control entity (520) to the first VNF instance (502), providing the obtained control message at least to the first and to the second VNF instances (502), and providing an acknowledgement of the control message to the control entity (520) when the interface element (510) has an acknowledgement, either explicit or implicit, of both the control message provided to the first VNF instance (502) and the control message provided to the second VNF instance (502).