The answer is to create a AAA group for RADIUS and reference it in the login default. The RADIUS server is reachable but not properly defined within a AAA group, so the router cannot send authentication requests despite the server being online. In CCNA 200-301 v2, this tests your understanding that the default group 'radius' must be explicitly configured with 'aaa group server radius RAD_GROUP' and a named server entry, otherwise the 'aaa authentication login default group radius local' command fails to engage the server. A common trap is assuming a reachable server automatically works with 802.1X, but without the group association, the port remains unauthorized. Remember: a server is just an IP until it’s in a group—group first, then authenticate.
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|dot1x|interface GigabitEthernet0/1
aaa new-model
aaa authentication login default group radius local
radius server RADIUS_SERVER
address ipv4 192.0.2.10 auth-port 1812 acct-port 1813
key Cisco123
!
interface GigabitEthernet0/1
description 802.1X Port
switchport mode access
authentication port-control auto
dot1x pae authenticator
spanning-tree portfast
!
R1# show authentication sessions interface GigabitEthernet0/1
Interface: GigabitEthernet0/1
MAC Address: 0050.7966.6800
IP Address: Unknown
Status: Unauthorized
Domain: DATA
Oper host mode: single-host
Oper control dir: both
Session timeout: N/A
Common Session ID: 0A0000010000000B00000001
Acct Session ID: 0x00000001
Handle: 0x81000001
R1# ping 192.0.2.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5)
R1# show radius server-group
Server group radius: not defined
You are connected to R1. Configure AAA with RADIUS server at 192.0.2.10 (key = Cisco123) so that console login uses local authentication as fallback. Then troubleshoot why a host connected to R1's GigabitEthernet0/1 (802.1X enabled) remains in unauthorized state. The RADIUS server is reachable. Fix the issue so the port authorizes successfully.
R1# show running-config | section aaa|radius|dot1x|interface GigabitEthernet0/1
aaa new-model
aaa authentication login default group radius local
radius server RADIUS_SERVER
address ipv4 192.0.2.10 auth-port 1812 acct-port 1813
key Cisco123
!
interface GigabitEthernet0/1
description 802.1X Port
switchport mode access
authentication port-control auto
dot1x pae authenticator
spanning-tree portfast
!
R1# show authentication sessions interface GigabitEthernet0/1
Interface: GigabitEthernet0/1
MAC Address: 0050.7966.6800
IP Address: Unknown
Status: Unauthorized
Domain: DATA
Oper host mode: single-host
Oper control dir: both
Session timeout: N/A
Common Session ID: 0A0000010000000B00000001
Acct Session ID: 0x00000001
Handle: 0x81000001
R1# ping 192.0.2.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5)
R1# show radius server-group
Server group radius: not defined
A
The RADIUS server is not defined in a AAA group; create 'aaa group server radius RAD_GROUP' and 'server name RADIUS_SERVER', then update the login default to reference the group.
This is correct because the 'aaa authentication login default group radius local' command references the default group 'radius', which must be explicitly defined with a RADIUS server. Without defining the group and associating the server, the router cannot communicate with the RADIUS server, causing authentication failures. Adding the group and updating the method list ensures the RADIUS server is used for 802.1X authentication.
B
The RADIUS server key is incorrect; change the key to match the server's configuration.
Why wrong: This is incorrect because the question states the RADIUS server is reachable, implying the key is correct. The issue is that the server is not defined in a AAA group, not a key mismatch.
C
The 802.1X port is not enabled; enable 'dot1x port-control auto' on GigabitEthernet0/1.
Why wrong: This is incorrect because the question states 802.1X is already enabled on the port. The issue is with AAA configuration, not port control.
D
The RADIUS server is not reachable; check IP connectivity and firewall rules.
Why wrong: This is incorrect because the question explicitly states the RADIUS server is reachable. The issue is not connectivity but the missing AAA group definition.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The RADIUS server is not defined in a AAA group; create 'aaa group server radius RAD_GROUP' and 'server name RADIUS_SERVER', then update the login default to reference the group.
The RADIUS server is reachable but not properly referenced in a AAA group. The 'aaa authentication login default group radius local' command uses the default group 'radius', which must be explicitly defined with 'aaa group server radius' and associated with the RADIUS server. Without this group, the router cannot send authentication requests to the server, keeping the port unauthorized. The fix is to create a AAA group for RADIUS, add the server to it, and update the login default to reference that group.
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 RADIUS server is not defined in a AAA group; create 'aaa group server radius RAD_GROUP' and 'server name RADIUS_SERVER', then update the login default to reference the group.
Why this is correct
This is correct because the 'aaa authentication login default group radius local' command references the default group 'radius', which must be explicitly defined with a RADIUS server. Without defining the group and associating the server, the router cannot communicate with the RADIUS server, causing authentication failures. Adding the group and updating the method list ensures the RADIUS server is used for 802.1X authentication.
Related concept
Authentication checks who the user is.
✗
The RADIUS server key is incorrect; change the key to match the server's configuration.
Why it's wrong here
This is incorrect because the question states the RADIUS server is reachable, implying the key is correct. The issue is that the server is not defined in a AAA group, not a key mismatch.
✗
The 802.1X port is not enabled; enable 'dot1x port-control auto' on GigabitEthernet0/1.
Why it's wrong here
This is incorrect because the question states 802.1X is already enabled on the port. The issue is with AAA configuration, not port control.
✗
The RADIUS server is not reachable; check IP connectivity and firewall rules.
Why it's wrong here
This is incorrect because the question explicitly states the RADIUS server is reachable. The issue is not connectivity but the missing AAA group definition.
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.
✓The RADIUS server is not defined in a AAA group; create 'aaa group server radius RAD_GROUP' and 'server name RADIUS_SERVER', then update the login default to reference the group.Correct answer▾
Why this is correct
This is correct because the 'aaa authentication login default group radius local' command references the default group 'radius', which must be explicitly defined with a RADIUS server. Without defining the group and associating the server, the router cannot communicate with the RADIUS server, causing authentication failures. Adding the group and updating the method list ensures the RADIUS server is used for 802.1X authentication.
✗The RADIUS server key is incorrect; change the key to match the server's configuration.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The key is already correct as per the scenario; the problem is the missing AAA group definition.
Why candidates choose this
Candidates often suspect key mismatches when RADIUS authentication fails, but here the server is reachable, so the key is not the issue.
✗The 802.1X port is not enabled; enable 'dot1x port-control auto' on GigabitEthernet0/1.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The port already has 802.1X enabled, so re-enabling it does not fix the authentication failure.
Why candidates choose this
Candidates might think the port is not properly configured for 802.1X, but the problem is at the AAA level, not the interface level.
✗The RADIUS server is not reachable; check IP connectivity and firewall rules.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The server is reachable, so connectivity is not the problem.
Why candidates choose this
Candidates often first suspect connectivity issues when RADIUS fails, but the scenario rules that out.
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.
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: The RADIUS server is not defined in a AAA group; create 'aaa group server radius RAD_GROUP' and 'server name RADIUS_SERVER', then update the login default to reference the group. — The RADIUS server is reachable but not properly referenced in a AAA group. The 'aaa authentication login default group radius local' command uses the default group 'radius', which must be explicitly defined with 'aaa group server radius' and associated with the RADIUS server. Without this group, the router cannot send authentication requests to the server, keeping the port unauthorized. The fix is to create a AAA group for RADIUS, add the server to it, and update the login default to reference that group.
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.
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. You are connected to R1. Configure AAA with a RADIUS server at 10.0.0.2/30 (key 'cisco123') so that console and VTY login use RADIUS first, then local authentication. Additionally, troubleshoot why an 802.1X-enabled switch port (GigabitEthernet0/1) on R1 is stuck in the unauthorized state. The RADIUS server is reachable but authentication fails. Verify using 'show aaa servers' and 'show dot1x interface GigabitEthernet0/1 details'.
hard
✓ A.Configure 'aaa authentication login default group RADIUS local' and correct the RADIUS server key to match the actual server key.
B.Configure 'aaa authentication login default group radius local' and verify the RADIUS server IP address is correct.
C.Configure 'aaa authentication login default group radius local' and enable 802.1X globally with 'dot1x system-auth-control'.
D.Configure 'aaa authentication login default local' and remove the RADIUS server configuration.
Why A: The RADIUS server is reachable but AAA and 802.1X authentication fail because the pre-shared key on R1 does not match the server's actual key. The correct repair is to first apply 'aaa authentication login default group RADIUS local' to correctly reference the RADIUS server by its name, then set the matching key under 'radius server RADIUS'. Once the key matches, the switch port will transition to authorized state.
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Question Discussion
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