The answer is network devices caching authentication responses, which is the most likely cause of RADIUS authentication caching after a password change. When a user changes their password in Active Directory, the RADIUS server forwards the new credentials to the directory for verification, but many network devices—such as switches and wireless controllers—store successful authentication responses locally in a cache to reduce load and latency. This cached response continues to accept the old password until the cache expires, typically within 30 minutes. On the CISSP exam, this scenario tests your understanding of authentication protocol behavior versus directory service integration; a common trap is assuming the RADIUS server itself caches credentials, but it usually acts as a pass-through proxy. Remember the memory tip: “Cache the device, not the server”—network devices hold the old response, while the RADIUS server queries the directory fresh each time.
CISSP Identity and Access Management Practice Question
This CISSP practice question tests your understanding of identity and access management. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company implements a centralized authentication system using RADIUS for network devices. The security team notices that after a user's password is changed in Active Directory, the user can still authenticate to network devices using the old password for up to 30 minutes. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Network devices caching authentication responses
Option C is correct because network devices often cache successful authentication responses, so they accept the old password until the cache expires. Option A is wrong because RADIUS servers typically forward authentication to the directory and do not cache credentials. Option B is wrong because it is not the primary cause in this scenario. Option D is wrong because Kerberos ticket lifetimes are unrelated to password changes in this context.
Key principle: Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Kerberos ticket lifetime
Why it's wrong here
Kerberos tickets are unrelated to password changes for RADIUS authentication.
✓
Network devices caching authentication responses
Why this is correct
Network devices often cache successful authentications, causing the old password to be accepted until cache expires.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Active Directory replication delay
Why it's wrong here
Replication delay could cause issues, but 30 minutes is long and caching is more likely.
✗
RADIUS server caching credentials
Why it's wrong here
RADIUS servers typically do not cache credentials; they forward to the directory.
Common exam traps
Common exam trap: authentication is not authorization
Logging in proves the user can authenticate. It does not automatically mean the user is allowed to enter privileged or configuration mode. Watch for AAA authorization, privilege level and command authorization details.
Detailed technical explanation
How to think about this question
This kind of question is testing the difference between identity and permission. A user may successfully log in to a router because authentication is working, but still fail to enter configuration mode because authorization is missing, misconfigured or mapped to a lower privilege level.
KKey Concepts to Remember
Authentication checks who the user is.
Authorization controls what the user is allowed to do after login.
Privilege levels affect access to EXEC and configuration commands.
AAA, TACACS+ and RADIUS can separate login success from command access.
TExam Day Tips
→Do not assume successful login means full administrative access.
→Look for words such as cannot enter configuration mode, privilege level, authorization or command access.
→Separate login problems from permission problems before choosing the answer.
Key takeaway
Authentication proves identity; authorization controls what that identity can do after login. Both must work for full privileged access.
Real-world example
How this comes up in practice
A SOC analyst notices unusual lateral movement in the network at 2 AM. The IR playbook dictates: identify and contain (isolate the affected machine), then eradicate (remove the malware), then recover (restore from backup), then document. Skipping containment before eradication risks the attacker regaining access. Questions like this test the sequence and rationale of incident response phases.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CISSP question in full detail.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CISSP questions on access control and AAA configuration.
Identity and Access Management — This question tests Identity and Access Management — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: Network devices caching authentication responses — Option C is correct because network devices often cache successful authentication responses, so they accept the old password until the cache expires. Option A is wrong because RADIUS servers typically forward authentication to the directory and do not cache credentials. Option B is wrong because it is not the primary cause in this scenario. Option D is wrong because Kerberos ticket lifetimes are unrelated to password changes in this context.
What should I do if I get this CISSP question wrong?
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related CISSP questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Authentication checks who the user is.
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