AZ-305 Design infrastructure solutions Practice Question
Your organization has a hybrid identity infrastructure with Microsoft Entra ID Connect Sync. You plan to enable Microsoft Entra ID Seamless Single Sign-On (Seamless SSO) for domain-joined Windows devices. What is the minimum requirement for the on-premises Active Directory forest functional level?
⚠ Common exam trap
Watch out — candidates often assume the minimum requirement is based on the operating system version of the domain controllers (e.g., Windows Server 2012 or 2016) rather than the forest/domain functional level, which is a separate configuration that controls available Kerberos encryption types and features.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Windows Server 2008
Microsoft Entra ID Seamless SSO works by having the client computer attempt Kerberos authentication against a local Active Directory domain controller using a special service principal name (AZUREADSSOACC). This process requires the on-premises Active Directory forest functional level to be at least Windows Server 2008, because the Kerberos service ticket used for Seamless SSO relies on the AES encryption type, which is only supported in domains with a Windows Server 2008 or higher functional level. Lower functional levels (2003 or earlier) do not support AES encryption, causing the authentication to fail.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Windows Server 2016
Why it's wrong here
Windows Server 2016 is fully capable of supporting Microsoft Entra ID Seamless SSO, but it is not the minimum requirement. The feature functions on any forest functional level from Windows Server 2008 upward, so choosing 2016 overstates the lowest possible level. Because the question specifically asks for the minimum, this higher-level option is incorrect despite being supported.
- ✗
Windows Server 2012
Why it's wrong here
Microsoft Entra ID Seamless SSO does support forests at the Windows Server 2012 functional level, so this is not a compatibility failure. The issue is that the question demands the minimum functional level, and 2012 is four versions newer than the actual 2008 threshold. Therefore, selecting 2012 would violate the 'minimum' constraint even though the feature would work in practice.
- ✓
Windows Server 2008
Why this is correct
Windows Server 2008 is the exact minimum forest functional level required to enable Microsoft Entra ID Seamless SSO. Microsoft's prerequisite documentation specifies that an on-premises forest must be at this level or higher, because the feature relies on Kerberos-based authentication and the creation of an AzureADKerberos computer account that is only supported on 2008 FFL and above. Thus, it is the only correct answer when identifying the minimum.
- ✗
Windows Server 2003
Why it's wrong here
At Windows Server 2003 functional level, Microsoft Entra ID Seamless SSO cannot function because the supporting Kerberos integration and the AzureADKerberos security principal are unavailable below the 2008 forest functional level. A 2003 domain can be synced with Microsoft Entra Connect, but the Seamless SSO feature explicitly requires a minimum FFL of Windows Server 2008. Consequently, this option fails both as a minimum and as a supported configuration.
Quick reference
Symmetric Encryption Algorithm Comparison
| Algorithm | Key Size | Block Size | Status | Notes |
|---|---|---|---|---|
| AES-128 | 128-bit | 128-bit | Current standard | NIST approved; WPA3, TLS |
| AES-256 | 256-bit | 128-bit | Current standard | Preferred for sensitive / govt data |
| 3DES | 112-bit effective | 64-bit | Deprecated (2023) | Replaced by AES |
| DES | 56-bit | 64-bit | Broken | Cracked in < 24 h; never deploy |
| ChaCha20 | 256-bit | Stream cipher | Current | TLS 1.3, WireGuard |
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-305 exam.