The correct answer is that the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without a local fallback method. When the RADIUS server at 198.51.100.10 is unreachable—due to a timeout or network issue—the switch has no alternative authentication source, so the port stays in an unauthorized state. This scenario tests your understanding of AAA RADIUS authentication fallback local 802.1X logic on the CCNA 200-301 v2 exam, where a common trap is configuring RADIUS as the sole method for dot1x while assuming local fallback is automatic. The fix requires modifying the dot1x authentication list to include 'local' as a secondary method, allowing the switch to authenticate the supplicant against the local user database (e.g., user 'admin') when the server is down. Remember: for 802.1X, always pair your RADIUS server with a local fallback—think "RADIUS first, local last" to avoid the unauthorized state trap.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and 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.
Exhibit
R1# show running-config | section aaa|radius|interface|line|username
username admin secret 5 $1$abc$defghijklmnopqrstuvwxyz12345
!
aaa new-model
aaa authentication login default group radius local
aaa authentication dot1x default group radius
!
radius server RADIUS
address ipv4 198.51.100.10 auth-port 1812 acct-port 1813
key cisco123
!
interface GigabitEthernet0/1
switchport mode access
authentication port-control auto
dot1x pae authenticator
!
line vty 0 4
login authentication default
transport input ssh
!
end
R1# show dot1x interface GigabitEthernet0/1 details
Dot1x Info for GigabitEthernet0/1
-----------------------------
PAE = AUTHENTICATOR
PortControl = AUTO
PortStatus = UNAUTHORIZED
ReAuthentication = Disabled
QuietPeriod = 60
ServerTimeout = 30
SuppTimeout = 30
ReAuthMax = 2
MaxReq = 2
TxPeriod = 30
AuthPeriod = 30
R1# show radius server-group all
Server group radius
Type: Standard
Member servers: RADIUS
VRF: default
R1# show radius server RADIUS
Radius server: RADIUS
Address: 198.51.100.10
Auth Port: 1812
Acct Port: 1813
Timeout: 5 seconds
Retransmit: 3
Key: cisco123
State: current UP
Dead: 0
Authentication: 0 requests, 0 timeouts, 0 failures
Accounting: 0 requests, 0 timeouts, 0 failures
You are connected to R1. Configure AAA with RADIUS authentication so that SSH users are authenticated first against the RADIUS server (198.51.100.10) and fall back to the local user database if the server is unreachable. Additionally, troubleshoot why an 802.1X-enabled interface (GigabitEthernet0/1) remains in the unauthorized state. The RADIUS server shares a key of 'cisco123' and uses UDP port 1812. The local user 'admin' with secret 'adminpass' must be available as a fallback.
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
R1# show running-config | section aaa|radius|interface|line|username
username admin secret 5 $1$abc$defghijklmnopqrstuvwxyz12345
!
aaa new-model
aaa authentication login default group radius local
aaa authentication dot1x default group radius
!
radius server RADIUS
address ipv4 198.51.100.10 auth-port 1812 acct-port 1813
key cisco123
!
interface GigabitEthernet0/1
switchport mode access
authentication port-control auto
dot1x pae authenticator
!
line vty 0 4
login authentication default
transport input ssh
!
end
R1# show dot1x interface GigabitEthernet0/1 details
Dot1x Info for GigabitEthernet0/1
-----------------------------
PAE = AUTHENTICATOR
PortControl = AUTO
PortStatus = UNAUTHORIZED
ReAuthentication = Disabled
QuietPeriod = 60
ServerTimeout = 30
SuppTimeout = 30
ReAuthMax = 2
MaxReq = 2
TxPeriod = 30
AuthPeriod = 30
R1# show radius server-group all
Server group radius
Type: Standard
Member servers: RADIUS
VRF: default
R1# show radius server RADIUS
Radius server: RADIUS
Address: 198.51.100.10
Auth Port: 1812
Acct Port: 1813
Timeout: 5 seconds
Retransmit: 3
Key: cisco123
State: current UP
Dead: 0
Authentication: 0 requests, 0 timeouts, 0 failures
Accounting: 0 requests, 0 timeouts, 0 failures
A
[CORRECT] The RADIUS server is unreachable, but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. The fix is to modify the dot1x authentication list to include 'local' as a fallback method.
This option correctly identifies that the server is unreachable and that the lack of local fallback prevents authentication via the local database. The recommended fix (adding 'local' to the dot1x authentication list) correctly resolves the issue.
B
The RADIUS server is unreachable because the shared key 'cisco123' is incorrect, causing the port to stay unauthorized.
Why wrong: This is incorrect because the RADIUS server is reachable (state UP), so the shared key is not the issue. The problem is the authentication list configuration, not server reachability.
C
The 802.1X port remains unauthorized because the RADIUS server uses UDP port 1812, but the switch expects port 1645.
Why wrong: This is incorrect because port 1812 is the standard RADIUS authentication port (UDP 1812 for authentication, 1813 for accounting). Cisco devices default to 1645 for authentication only in legacy configurations, but modern IOS uses 1812 by default.
D
The SSH authentication fails because the local user 'admin' is not configured with the correct privilege level, so fallback does not work.
Why wrong: This is incorrect because the SSH authentication is working correctly with the 'aaa authentication login default group radius local' command. The local user 'admin' is available, and fallback works. The issue is only with 802.1X, not SSH.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
[CORRECT] The RADIUS server is unreachable, but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. The fix is to modify the dot1x authentication list to include 'local' as a fallback method.
The RADIUS server is unreachable (not reachable), but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. When the server cannot be reached (e.g., timeout), no fallback exists, so the port stays unauthorized. The fix is to modify the dot1x authentication list to include 'local' as a fallback method. Adding local fallback allows the switch to authenticate the supplicant using the local database when the RADIUS server is unreachable.
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.
✓
[CORRECT] The RADIUS server is unreachable, but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. The fix is to modify the dot1x authentication list to include 'local' as a fallback method.
Why this is correct
This option correctly identifies that the server is unreachable and that the lack of local fallback prevents authentication via the local database. The recommended fix (adding 'local' to the dot1x authentication list) correctly resolves the issue.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
The RADIUS server is unreachable because the shared key 'cisco123' is incorrect, causing the port to stay unauthorized.
Why it's wrong here
This is incorrect because the RADIUS server is reachable (state UP), so the shared key is not the issue. The problem is the authentication list configuration, not server reachability.
✗
The 802.1X port remains unauthorized because the RADIUS server uses UDP port 1812, but the switch expects port 1645.
Why it's wrong here
This is incorrect because port 1812 is the standard RADIUS authentication port (UDP 1812 for authentication, 1813 for accounting). Cisco devices default to 1645 for authentication only in legacy configurations, but modern IOS uses 1812 by default.
✗
The SSH authentication fails because the local user 'admin' is not configured with the correct privilege level, so fallback does not work.
Why it's wrong here
This is incorrect because the SSH authentication is working correctly with the 'aaa authentication login default group radius local' command. The local user 'admin' is available, and fallback works. The issue is only with 802.1X, not SSH.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓[CORRECT] The RADIUS server is unreachable, but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. The fix is to modify the dot1x authentication list to include 'local' as a fallback method.Correct answer▾
Why this is correct
This option correctly identifies that the server is unreachable and that the lack of local fallback prevents authentication via the local database. The recommended fix (adding 'local' to the dot1x authentication list) correctly resolves the issue.
✗The RADIUS server is unreachable because the shared key 'cisco123' is incorrect, causing the port to stay unauthorized.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The shared key is used for encrypting RADIUS traffic, but server reachability is confirmed; the key mismatch would cause authentication failures, not port unauthorized state due to missing fallback.
Why candidates choose this
Candidates often confuse shared key issues with authentication list configuration, assuming any RADIUS problem is due to key mismatch.
✗The 802.1X port remains unauthorized because the RADIUS server uses UDP port 1812, but the switch expects port 1645.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The question states the server uses UDP port 1812, which is correct. The switch would need explicit configuration to use 1645; default is 1812.
Why candidates choose this
Candidates may recall that older Cisco devices used port 1645, leading them to think a port mismatch is the cause.
✗The SSH authentication fails because the local user 'admin' is not configured with the correct privilege level, so fallback does not work.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: Privilege level is not required for authentication; it affects authorization. The local user exists and can authenticate, so SSH fallback is fine.
Why candidates choose this
Candidates may think that local fallback requires specific privilege levels, but authentication only needs a valid username/password.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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.
Trap categories for this question
Command / output trap
This is incorrect because the SSH authentication is working correctly with the 'aaa authentication login default group radius local' command. The local user 'admin' is available, and fallback works. The issue is only with 802.1X, not SSH.
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 junior network technician can log in to a core router but cannot reach the enable prompt or configuration mode. The AAA server is authenticating the login — but the authorisation policy only grants privilege level 1, not 15. Authentication (who you are) is working; authorisation (what you can do) is not.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 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 200-301 questions on access control and AAA configuration.
Network Services and Security — This question tests Network Services and Security — Authentication checks who the user is..
What is the correct answer to this question?
The correct answer is: [CORRECT] The RADIUS server is unreachable, but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. The fix is to modify the dot1x authentication list to include 'local' as a fallback method. — The RADIUS server is unreachable (not reachable), but the 802.1X port remains unauthorized because the AAA authentication list for dot1x is configured to use only RADIUS without local fallback. When the server cannot be reached (e.g., timeout), no fallback exists, so the port stays unauthorized. The fix is to modify the dot1x authentication list to include 'local' as a fallback method. Adding local fallback allows the switch to authenticate the supplicant using the local database when the RADIUS server is unreachable.
What should I do if I get this 200-301 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 200-301 questions on access control and AAA configuration.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Authentication checks who the user is.
About these practice questions
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Variation 1. You are connected to R1. Configure AAA with RADIUS authentication on R1 so that SSH login attempts first contact the RADIUS server at 192.0.2.10 (key 'cisco123'), and if the server is unreachable, fall back to the local database. Additionally, troubleshoot why an 802.1X-enabled switch port (GigabitEthernet0/1) on a connected switch remains in the 'unauthorized' state despite RADIUS being functional; identify and fix the misconfiguration on the switch (SW1).
Why A: The correct answer is Option A. For R1, the 'aaa authentication login default group radius local' command ensures that SSH login attempts first contact the RADIUS server at 192.0.2.10 and fall back to the local database if the server is unreachable. Options that omit the 'local' keyword (C) lack this fallback, making them incorrect. Option B incorrectly uses 'aaa authentication login' on the switch for 802.1X; the correct command is 'aaa authentication dot1x'. On SW1, all wrong options (B, C, D) are missing the 'dot1x pae authenticator' command under the interface, which is required for the switch to explicitly act as an 802.1X authenticator (though some IOS versions auto-assume it, Cisco CCNA expects explicit configuration). Option D also lacks 'dot1x pae authenticator', leaving the port in unauthorized state. Only Option A includes all necessary commands: correct RADIUS server definitions, proper AAA authentication lists for both login and dot1x, global 'dot1x system-auth-control', and the interface-level commands 'authentication port-control auto' and 'dot1x pae authenticator'.
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