How to properly organize AD, DNS, DHCP branch?

Question

Active Directory

Organize a branch.
To work, we raise the second Domain Controller (for communication we set up an ipsec tunnel and write routes on the router)
How to properly organize the work of DNS and DHCP in the branch so as not to overload the central office network and not interrupt the work of the branch when the tunnel breaks?
those. the branch needs a completely autonomous system, the data is synchronized with the CO, but if the tunnel falls, it continues to work without failures

Answer 1

1. Allocate a separate subnet for the branch. Set up IPSec and routing.
   The branch office computers are synchronized with the local domain controller, which in turn is synchronized with the controllers at the head office. Autonomy is preserved, since information about policies and credentials, DHCP and DNS is physically in the branch.

Answer 2

https://duckduckgo.com/?q=%D0%BC%D0%B5%D0%B6%D1%81...

Answer 3

the branch needs a fully autonomous system

Make your domain trust relationship with the head office domain.