A method for determining a termination point of at least one tunnel or segment in a packet switching network. The network includes a set of routers and links between them, the routers and links forming a previous network topology, a transit router receiving packets intended for an output router, an event modifying the previous topology into a subsequent network topology, and a backup path between the transit router and the output router being calculated for the subsequent topology. The method includes calculating, prior to the event, for each router, an initial tree based on the previous topology, which has as a root the router and has as branches paths of minimum cost between the root and the other routers. A termination point of a tunnel or segment is obtained to prevent packets transiting between the start router and the output router from entering into a micro-loop caused by the event.