A system, computer program, computer-readable medium and method for providing a redundant relay, particularly routing function in a network, wherein a superordinate subnetwork is connected to a subordinate subnetwork via redundant relays, particularly routers, a maximum of one of the redundant relays is operated in an active mode at any one time, while the remaining relay(s) are in standby mode, each redundant relay forms a relay redundancy module for controlling the relay mode and a DHCPv6 client for processing a prefix delegation, particularly in accordance with RFC 3633, and the redundant relays each include a relay control module, to which the relay redundancy module of the particular relay signals the current relay mode, and the relay control module of the active relay synchronizes a virtual DUID of its DHCPv6 client and/or a prefix delegated to the active relay to the (or each) relay in standby mode.