The answer is a RADIUS timeout value that is too low on the Cisco Catalyst 3850 switch. This is the most likely cause because the intermittent nature of the failures—where users connect successfully one day but fail the next—points to a timeout threshold that is barely adequate under low latency but insufficient during brief periods of network congestion or ISE processing delay. When the switch’s RADIUS timeout expires before the full PEAP-MSCHAPv2 EAP conversation completes, it drops the mid-exchange packets, generating the EAP timeout errors in the switch logs while ISE logs show no authentication failure. On the Cisco SCOR 350-701 exam, this scenario tests your understanding of how RADIUS timers interact with multi-round EAP exchanges; a common trap is to blame ISE performance or switch hardware when the real issue is a misconfigured timeout. Remember the mnemonic: “EAP is chatty, so your timeout must be chatty too”—if the timeout is too short, the switch hangs up before the conversation finishes.
350-701 Network Security Practice Question
This 350-701 practice question tests your understanding of network security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 large enterprise uses Cisco ISE for network access control with 802.1X authentication (PEAP-MSCHAPv2) on wired ports. Access switches are Cisco Catalyst 3850s running IOS-XE 16.9, and ISE is version 2.7 with all patches. Recently, users in the finance department report intermittent connectivity issues when connecting to the network. The issue is sporadic: a user may connect successfully one day, then fail multiple times the next day. Switch logs show frequent 'EAP timeout' errors for these users. The network team has verified that the RADIUS servers are reachable and have sufficient CPU and memory. The ISE logs show no authentication failures, only that some EAP conversations are dropped mid-exchange. What is the most likely cause of these intermittent failures?
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.
The switch is configured with a RADIUS timeout value that is too low.
A low timeout can cause the switch to abort EAP exchanges when network latency spikes, leading to intermittent timeouts.
B
The switch port is configured with a dynamic VLAN assignment that does not exist on the switch.
Why wrong: This would cause consistent failure for users assigned to that VLAN, not intermittent.
C
The user's machine certificate has expired.
Why wrong: PEAP-MSCHAPv2 does not use client certificates; it uses machine credentials. Even if it did, expired certificates cause consistent failures.
D
The ISE server is configured with an incorrect shared secret for the switch.
Why wrong: An incorrect shared secret would cause all authentications to fail consistently.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The switch is configured with a RADIUS timeout value that is too low.
The EAP timeout errors and intermittent nature point to the RADIUS timeout being too low on the switch, causing it to drop EAP conversations during periods of high latency. Options A, B, and D would cause consistent failures for affected users, not intermittent issues.
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.
✓
The switch is configured with a RADIUS timeout value that is too low.
Why this is correct
A low timeout can cause the switch to abort EAP exchanges when network latency spikes, leading to intermittent timeouts.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
The switch port is configured with a dynamic VLAN assignment that does not exist on the switch.
Why it's wrong here
This would cause consistent failure for users assigned to that VLAN, not intermittent.
✗
The user's machine certificate has expired.
Why it's wrong here
PEAP-MSCHAPv2 does not use client certificates; it uses machine credentials. Even if it did, expired certificates cause consistent failures.
✗
The ISE server is configured with an incorrect shared secret for the switch.
Why it's wrong here
An incorrect shared secret would cause all authentications to fail consistently.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
Review Cisco AAA concepts — authentication, authorization, and accounting. Study privilege levels (0–15), command authorization under TACACS+, and how RADIUS differs. Then practise related 350-701 questions on access control and AAA configuration.
Network Security — This question tests Network Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: The switch is configured with a RADIUS timeout value that is too low. — The EAP timeout errors and intermittent nature point to the RADIUS timeout being too low on the switch, causing it to drop EAP conversations during periods of high latency. Options A, B, and D would cause consistent failures for affected users, not intermittent issues.
What should I do if I get this 350-701 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 350-701 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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A university is deploying 802.1X authentication for wired access using Cisco ISE. The network consists of Cisco Catalyst switches. The authentication is working for most users, but some users in a specific building are experiencing frequent authentication failures, especially during peak hours. The switches in that building are configured with RADIUS settings pointing to ISE. ISE logs show that authentication requests are being sent but sometimes time out. The network team suspects that the issue is related to RADIUS server load balancing, as the ISE deployment includes two nodes in a distributed model. What is the most likely cause of the timeouts?
hard
A.The RADIUS shared secret is misconfigured on some switches.
B.The switches are not configured with the correct VLAN assignments.
C.The switches are using the wrong RADIUS accounting port.
✓ D.The ISE nodes are not configured for load balancing, causing one node to be overwhelmed.
Why D: Option D is correct because the symptoms—intermittent timeouts during peak hours in a specific building—point to a load-balancing issue. In a distributed ISE deployment, if the switches are not configured with multiple RADIUS server entries or if ISE nodes are not properly load-balanced (e.g., using a single primary server or missing secondary server configuration), one node can become overwhelmed with authentication requests, leading to timeouts. The fact that authentication works for most users but fails during peak hours in one building strongly suggests that the switches in that building are sending all requests to a single ISE node that cannot handle the load.
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Question Discussion
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