How to install Sql Server Data Tools (SSDT) 2017 Offline (Internal Network installation)

Folks thanks for reporting the problem with installation. I reproduced the problem and examined the log file

[0B9C:3BD4][2021-10-12T12:07:18]e000: Error 0x80070002: Failed attempt to download URL: 'https://go.microsoft.com/fwlink/?LinkId=874726' to: 'C:\Users\joseph\AppData\Local\Temp\{7D87F596-B564-4EC7-BABE-06EFFF5EFBBF}\VCRedist2010'
[0B9C:3BD4][2021-10-12T12:07:18]e000: Error 0x80070002: Failed to acquire payload from: 'https://go.microsoft.com/fwlink/?LinkId=874726' to working path: 'C:\Users\joseph\AppData\Local\Temp\{7D87F596-B564-4EC7-BABE-06EFFF5EFBBF}\

The issue is that the URL https://go.microsoft.com/fwlink/?LinkId=874726 is no longer valid.

Solution: 

The SSDT-Setup-ENU.exe has been updated to contain all the information inside it and is therefore a larger file. But you can follow the steps on DOCs for offline install which will allow you to proceed successfully

The instructions above have also been updated as of this Comment