A method for use by a router in a communications network, comprising: (a) maintaining forwarding information specifying the next hop node for each of a plurality of possible destination nodes; (b) maintaining update information specifying how, if at all, the next hop nodes specified in the forwarding information are to be updated for a plurality of possible network resource failures; (c) maintaining known failure information relating to a known network resource failure or specifying that there is no known network resource failure; (d) receiving a failure notification relating to a network resource failure, and in response to receipt of the failure notification: (i) determining from the failure notification how, if at all, the known failure information is to be updated; (ii) updating the known failure information, if required, based on the determination; (e) receiving a communications packet, and in response to receipt of the communications packet: (i) determining the destination node for the received packet; (ii) determining whether the next hop node specified by the forwarding information for the determined destination node is potentially invalid in view of the known failure information; (iii) if so, then updating if necessary the next hop node for the determined destination node in the forwarding information using the update information and the known failure information; (iv) determining the next hop node for the received packet using the forwarding information and the determined destination node; and (v) forwarding the received packet towards the determined next hop node. (a) maintaining forwarding information specifying the next hop node for each of a plurality of possible destination nodes; (b) maintaining update information specifying how, if at all, the next hop nodes specified in the forwarding information are to be updated for a plurality of possible network resource failures; (c) maintaining known failure information relating to a known network resource failure or specifying that there is no known network resource failure; (d) receiving a failure notification relating to a network resource failure, and in response to receipt of the failure notification: (i) determining from the failure notification how, if at all, the known failure information is to be updated; (ii) updating the known failure information, if required, based on the determination; (i) determining from the failure notification how, if at all, the known failure information is to be updated; (ii) updating the known failure information, if required, based on the determination; (e) receiving a communications packet, and in response to receipt of the communications packet: (i) determining the destination node for the received packet; (ii) determining whether the next hop node specified by the forwarding information for the determined destination node is potentially invalid in view of the known failure information; (iii) if so, then updating if necessary the next hop node for the determined destination node in the forwarding information using the update information and the known failure information; (iv) determining the next hop node for the received packet using the forwarding information and the determined destination node; and (v) forwarding the received packet towards the determined next hop node. (i) determining the destination node for the received packet; (ii) determining whether the next hop node specified by the forwarding information for the determined destination node is potentially invalid in view of the known failure information; (iii) if so, then updating if necessary the next hop node for the determined destination node in the forwarding information using the update information and the known failure information; (iv) determining the next hop node for the received packet using the forwarding information and the determined destination node; and (v) forwarding the received packet towards the determined next hop node.