You have an Azure Active Directory (Azure AD) tenant.
All administrators must enter a verification code to access the Azure portal.
You need to ensure that the administrators can access the Azure portal only from your on-premises network.
What should you configure?
The security of two-step verification lies in its layered approach. Compromising multiple authentication factors presents a significant challenge for attackers. Even if an attacker manages to learn the user's password, it is useless without also having possession of the additional authentication method. It works by requiring two or more of the following authentication methods:
Something you know (typically a password).
Something you have (a trusted device that is not easily duplicated, like a phone).
Something you are (biometrics).