A first router in a first AS, the first router comprises: a processor configured to: obtain information about a broadcast link connecting the first router to a second router in a second AS, and generate a link state message comprising the information; and a transmitter coupled to the processor and configured to transmit the link state message to a third router, wherein the third router is in the first AS and is adjacent to the first router. A method comprises: receiving a first link state message from a first router; receiving a second link state message from a second router; receiving a third link state message from a third router; determining which of the first router, the second router, and the third router are ASBRs connected to a broadcast link based on information in the first link state message, the second link state message, and the third link state message.