The invention relates to a system for protecting a communications network comprising a transport network (3) and end-channel equipment (1) such as routers each connected to said transport network (3) by connecting sections wherein said protective system is provided with first and second protective systems. Said invention is characterised in that for each communications channel between two pieces of said end-channel equipment (1), the first protective system is activated when a failure is detected in said transport network (3) which emits a direct channel alarm message (AU-AIS) to equipment on the downstream end thereof, said second protective system is activated, after detection by end equipment of said channel (1) of a failure in the connection section connecting it to said transport network or when equipment (1) of the downstream end of said channel receives the direct or indirect alarm message (AU-AIS, AU-RDI) emitted by the transport network and the second protective system is activated, after reception of the direct alarm message (AU-AIS), with a delay longer than after detection of the failure on a second connection section between said transport network (3) and end-channel equipment (1). A protection method carried out by said protective system is also disclosed.