A network transfers a first packet addressed to a first address and indicating a second address. The network routes the first packet through a first set of routers. The first routers transfer route priority messages indicating the second address to directly linked routers to lower their route priority to the first routers for the second address. The network transfers a second packet addressed to the second address and indicating the first address. The network routes the second packet through a second set of routers. The second routers transfer route priority messages indicating the first address to directly linked routers to lower their route priority to the second routers for the first address. The network routes a first packet flow addressed to the first address through the first routers and routes a second packet flow addressed to the second address through the second routers.