A method of generating network identifiers for use by mobile routers of a moving network is provided which enables fast and efficient routing loop avoidance and detection. The method comprises receiving at a mobile router of a sub-network chain, a beacon from a preceding mobile router in the chain, the beacon containing a network identifier of the preceding mobile router, generating a new network identifier by applying a pre-defined function to the received network identifier, and including the new network identifier in beacons broadcast by the receiving mobile router. When preparing for a handover, a mobile router compares the network identifier contained in a received beacon with values generated by applying said function against its own network identifier. This allows the mobile router to identify beacons originating from mobile routers that are downstream in the same chain.