There are now many OSes that put the network to sleep to save power so it's never a sure thing they will respond to pings or other network traffic.
This is proper and working as expected. It can be upsetting to your newer network admins.
When I try to scan my network(wifi) by n-map or any other software the hosts(mobile and PC) on my network sometimes are detected but most of the time they go undetected .They only show up when I browse internet on them.Overall the detection is unstable .WHY is this happening ? and How can I stop it ?

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