A few weeks, restarts, and at least one system update ago, my M1 MacBook Air developed a new behavior. Apparently kernel_task has sessions of communication with the Ethernet-connected Time Capsule, sending about 2-5 MB/sec and receiving about 0.5-1 MB/sec. It will do this for about 20 minutes, then take a 15 minute break, then repeat.
The Time Capsule is not connected to the internet. (It does have a printer attached, but the printer does not wake up for these sessions.) The activity takes place whether Wi-Fi (internet) is on or off, but stops abruptly and resumes promptly when I make the Ethernet service inactive and active. I believe it is kernel_task because Activity Monitor shows that process as active (10-20%) and the Sent Packets and Received Packets for that process continually increment when the network activity is as I described. Typically, Time Machine shows no active backup. (At least once, the kernal_task communication was ongoing when a Time Machine backup started, and the two seemed to run concurrently.)
The MBA was running macOS 11.4, and the behavior might have started immediately after I installed 11.4. I installed macOS 11.5.1 recently, and the behavior continues. Any ideas what this might be? Or what I should do about it? Thanks.