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Abstract

The invention is related to structures used for providing fault tolerance in computer data networks. According to the invention, fault tolerance is achieved by redundancy, i.e. by using at least two network nodes in parallel. The network nodes have at least two physical network interface to a network, only one of which is active during normal operation. In the case of two network nodes being used, both of these have two physical network interfaces to the same network. A first network interfaces on the first node has the same IP and MAC address as one interface on the second node, and the second network interface on the first node has the same IP and MAC address as the other interface on the second node. The IP and MAC addresses of the two interfaces of each node are different, whereby the two nodes provide a first IP address and a corresponding first MAC address, and a second IP address and a corresponding second MAC address. In normal operation, a first node of the two nodes handles traffic directed to the first IP address and ignores the traffic directed to the second IP address, and the second node handles traffic directed to the second IP address and ignores the traffic directed to the first IP address. The two nodes monitor each other for fault conditions, and if one of the nodes show signs of failure, the other node activates the other of its interfaces and starts handling traffic directed to both IP addresses.

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First Claim