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Which layer and protocol takes care of power-down and power-up of ethernet port (based on cable connected or disconnected) in a Linux machine.
I think it (power-up and power-down) will be taken care by Physical layer and MAC layer.

  1. Are these layers implemented in Linux network drivers or as TCP_IP stack in the Linux Kernel?
  2. Is there a way to bypass those protocols (responsible for Power-down Ethernet port) to make the Ethernet port to stay Power-up always even if no cable connected to the port.

Some one please answer,

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Are these layers implemented in Linux network drivers or as TCP_IP stack in the Linux Kernel?

The IEEE 802.3 (i.e. Ethernet) standards define operation in both L1 and L2 of the OSI model (L1 or L1/L2 depending on where you source your TCP/IP model).

Typically, much of the L1/L2 802.3 standards are implemented in the hardware of the network interface, especially the most basic of functions. There is no reason to task the OS/CPU with processing decisions of this nature so doing so in hardware leaves the CPU idle to handle other processing.

Is there a way to bypass those protocols (responsible for Power-down Ethernet port) to make the Ethernet port to stay Power-up always even if no cable connected to the port.

You can disable or power down the NIC, but aside from that in effect it is always "powered up" even when there is no cable connected. While power is granted to the NIC, the issue is that without a cable connected, there is no completed circuit to utilize that power.

As an example, consider a simple circuit such as a light bulb connected to a switch. You can turn the switch on, but if one of the wires going from the switch to the light bulb isn't connected, the bulb isn't "up" and the power is not in use even though the switch is on. Once you connect the wire, the power will start to be used and the bulb will be "up" or turn on.

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