I have downloaded all the VS packages ( around 35 GB) using the below command line.
vs_community.exe --layout c:\vslayout --lang en-US
Now, I use the command vs_community.exe --noweb to install in a PC with no internet connection. As the installer option is offline mode, but still the installer says not connected to internet.
To help improve the issue, I add an answer here. Also, thanks to Martheen for sharing the info.
Answer
You have to install certificates from the offline package to install the VS because the new environment is offline and cannot get the requests and permissions for installing VS.
So you have to open the certificates folder of the offline package to install them one by one to get that.
You can refer to this for more info.
Update 1
use a bat file to execute the offline installation of VS.
certmgr.exe -add [layout path]\certificates\manifestRootCertificate.cer -n "Microsoft Root Certificate Authority 2011" -s -r LocalMachine root
.....
//add any for certs
vs_community.exe --noweb