A switch for an avionics communication system comprising a plurality of end systems (24A,..., 24N) transmitting digital data in the form of frames according to a data transmission protocol of the Ethernet type with predetermined routing, each frame comprising an identifier and an observation configuration field; the switch including: - a plurality of input ports, each input port being able to receive frames coming from one of the end systems (24A,...,24N) or another switch (22B,...,22N); - a plurality of output ports, each output port being able to transmit frames to one of the end systems (24A,...,24N) or another switch (22B,...,22N), at least one output port, called observation port, being connected to an observation module arranged in the one of the end systems (24A,..., 24N) and able to analyze the traffic of the frames passing through via the switch; - a conveying component configured to convey each frame according to said transmission protocol between at least one input port and one or several output ports; each input and output port being associated with an identifier; the switch being configured to transmit, to the observation module via the observation port, only frames according to a first observation condition and a second observation condition; the compliance of a frame with the first observation condition being determined as a function of the observation configuration field of this frame and the compliance with the second observation condition being determined as a function of the identifier of this frame and/or of an input and/or one of the output ports associated with this frame, wherein the observation configuration field of each frame defines an observation access level of this frame, the compliance with the second observation condition being determined as a function of this access level and one or several outside parameters, preferably relative to the operation of the avionics communication system and/or the observation module. the switch including: - a plurality of input ports, each input port being able to receive frames coming from one of the end systems (24A,...,24N) or another switch (22B,...,22N); - a plurality of output ports, each output port being able to transmit frames to one of the end systems (24A,...,24N) or another switch (22B,...,22N), at least one output port, called observation port, being connected to an observation module arranged in the one of the end systems (24A,..., 24N) and able to analyze the traffic of the frames passing through via the switch; - a conveying component configured to convey each frame according to said transmission protocol between at least one input port and one or several output ports; - a plurality of input ports, each input port being able to receive frames coming from one of the end systems (24A,...,24N) or another switch (22B,...,22N); - a plurality of output ports, each output port being able to transmit frames to one of the end systems (24A,...,24N) or another switch (22B,...,22N), at least one output port, called observation port, being connected to an observation module arranged in the one of the end systems (24A,..., 24N) and able to analyze the traffic of the frames passing through via the switch; - a conveying component configured to convey each frame according to said transmission protocol between at least one input port and one or several output ports; each input and output port being associated with an identifier; the switch being configured to transmit, to the observation module via the observation port, only frames according to a first observation condition and a second observation condition; the compliance of a frame with the first observation condition being determined as a function of the observation configuration field of this frame and the compliance with the second observation condition being determined as a function of the identifier of this frame and/or of an input and/or one of the output ports associated with this frame, wherein the observation configuration field of each frame defines an observation access level of this frame, the compliance with the second observation condition being determined as a function of this access level and one or several outside parameters, preferably relative to the operation of the avionics communication system and/or the observation module.