Patent ID: 8014399

Claim:
A method of operating a data network, of the type in which a number of interconnected router devices forward received packets of data towards a destination node in accordance with a routing table associated with each router, the method comprising: receiving routing information at one of said routers; determining at the router if the information is such that, if it were correct, it would cause the router to update its routing table in respect of one or more entries, and, if so, sending out from the router two test packets, one of which is sent out by the router according to the existing information contained in the router's routing table and the other of which is sent out by the router according to the information which would be included in the routing table if it were updated in accordance with the received information; comparing at the router the results of the two test sendings; and updating by the router of the routing table to reflect the received information if the comparison by the router indicates that the information received by the router is correct, but otherwise the router ignoring the information and maintaining the routing table unchanged.