How do I stop internet traffic while in sleep on iMac?

I have IMac (Mojave) and recently acquired M1 silicon (Sequoia) attached to same router via ethernet cables.

Both ports on the router say 1000Mbps.

When the IMac goes to sleep its ethernet port shows disconnected and the TX and RX numbers stop increasing.

When M1 goes to ‘sleep’? (that is when the screen goes to sleep) the router port is still connected but gone from 1000 Mbps to 100 Mbps.

Both the TX & RX bytes/packets keep increasing on the M1 port.

In System settings/Energy on the M1 I have all options deselected i.e.:

• Prevent automatic sleeping when display is off;
• Wake on network access; and
• Start up automatically after power failure.

I would like to set up the M1 the same way as the IMac so that there is NO traffic in or out when in sleep.

I do not care whom the M1 is talking to or why I just want it to be invisible while in sleep mode.

I appreciate some people won’t think this is a concern but it is for me hence why I ask:

Other than disconnecting M1 either in the settings or physically removing the cable is there a way to set the M1 so its router port is ‘disconnected’ when in sleep, as happens with the Imac?

[Re-Titled by Moderator]

Original Title: Stopping internet traffic while in Sleep