Google analytics for main domain and subdomains?

Question

Google Analytics

There is a site for example: mysite.ru , some sections of which are available through a subdomain, for example: phones.mystite.ru
The site has analytics installed through Google Tag Manager .
When mysite.ru or phones.mystite.ru is accessed, there is no difference in analytics:

i.e. it is impossible to understand - whether there was a call to pages on a subdomain or on the main domain
How to implement subdomain analytics?

Answer 1

https://support.google.com/analytics/answer/103434...