The answer is to enable AAA with the global command aaa new-model, then configure a RADIUS server named RADIUS_SERVER with the key cisco123 and IP 192.0.2.10, and finally apply aaa authentication login default group radius local. This is correct because without aaa new-model, the router cannot process AAA commands at all, and without a defined RADIUS server, the router has no way to forward authentication requests for 802.1X or login access. On the CCNA 200-301 v2 exam, this scenario tests your understanding that AAA configuration is a prerequisite for any RADIUS-based authentication, and a common trap is forgetting to issue aaa new-model first or omitting the local fallback keyword, which would lock out administrators if the RADIUS server is unreachable. A useful memory tip is "New model first, then server, then list"—always enable AAA globally before defining the RADIUS server and authentication method list.
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
no aaa new-model
!
R1# show running-config | section radius
!
R1# show running-config interface GigabitEthernet0/1
interface GigabitEthernet0/1
description 802.1X port
switchport mode access
switchport access vlan 10
authentication port-control auto
dot1x pae authenticator
spanning-tree portfast
!
R1# show authentication sessions interface GigabitEthernet0/1
Interface: GigabitEthernet0/1
MAC Address: aaaa.bbbb.cccc
IP Address: unknown
Status: Unauthorized
Domain: DATA
Oper host mode: single-host
Oper control dir: both
Session timeout: N/A
Common Session ID: 0A0000010000000100000001
Acct Session ID: 0x00000001
Handle: 0x51000001
R1# test aaa group radius legacy aaaa.bbbb.cccc password cisco123
Trying to authenticate with server group radius
User authentication request was rejected by server
R1# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 203.0.113.1 YES NVRAM up up
GigabitEthernet0/1 unassigned YES unset up up
Loopback0 10.10.10.1 YES NVRAM up up
You are connected to R1, a router acting as a network access server for 802.1X authentication on interface GigabitEthernet0/1. Configure AAA with a RADIUS server at 192.0.2.10 (key 'cisco123') so that the default login authentication uses RADIUS first, then local fallback. Additionally, troubleshoot why a connected supplicant on G0/1 remains in the unauthorized state even though RADIUS is reachable and the supplicant credentials are correct.
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
no aaa new-model
!
R1# show running-config | section radius
!
R1# show running-config interface GigabitEthernet0/1
interface GigabitEthernet0/1
description 802.1X port
switchport mode access
switchport access vlan 10
authentication port-control auto
dot1x pae authenticator
spanning-tree portfast
!
R1# show authentication sessions interface GigabitEthernet0/1
Interface: GigabitEthernet0/1
MAC Address: aaaa.bbbb.cccc
IP Address: unknown
Status: Unauthorized
Domain: DATA
Oper host mode: single-host
Oper control dir: both
Session timeout: N/A
Common Session ID: 0A0000010000000100000001
Acct Session ID: 0x00000001
Handle: 0x51000001
R1# test aaa group radius legacy aaaa.bbbb.cccc password cisco123
Trying to authenticate with server group radius
User authentication request was rejected by server
R1# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 203.0.113.1 YES NVRAM up up
GigabitEthernet0/1 unassigned YES unset up up
Loopback0 10.10.10.1 YES NVRAM up up
A
Enable AAA with 'aaa new-model', configure RADIUS server 'RADIUS_SERVER' with key 'cisco123', and apply 'aaa authentication login default group radius local'.
This is correct because 'aaa new-model' enables AAA services, the RADIUS server configuration defines the server and key, and the default login authentication list uses RADIUS first with local fallback. Without these, 802.1X cannot authenticate.
B
Configure 'aaa authentication login default local' and add the RADIUS server with 'radius-server host 192.0.2.10 key cisco123'.
Why wrong: This is incorrect because the authentication list uses only local authentication, not RADIUS first. The RADIUS server is configured but never referenced in the authentication list, so RADIUS is not used.
C
Enable AAA with 'aaa new-model' and configure 'aaa authentication login default group radius' without local fallback.
Why wrong: This is incorrect because there is no local fallback; if the RADIUS server is unreachable, authentication fails entirely. The requirement specifies local fallback.
D
Configure 'aaa new-model', then apply 'dot1x system-auth-control' and 'aaa authentication dot1x default group radius'.
Why wrong: This is incorrect because the question asks for default login authentication, not dot1x authentication. The 'aaa authentication login' command is for login (management access), while 'aaa authentication dot1x' is for 802.1X port authentication. The problem is about login authentication, not dot1x authentication list.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable AAA with 'aaa new-model', configure RADIUS server 'RADIUS_SERVER' with key 'cisco123', and apply 'aaa authentication login default group radius local'.
The problem is that AAA is not enabled (no aaa new-model) and no RADIUS server is configured; thus the 802.1X authentication fails because the router does not know how to communicate with the RADIUS server. The fix requires enabling AAA with 'aaa new-model', configuring the RADIUS server with 'radius server RADIUS_SERVER' and its key, then applying a default authentication list that uses RADIUS with local fallback via 'aaa authentication login default group radius local'. After these commands, the port should transition to authorized state for valid credentials.
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.
✓
Enable AAA with 'aaa new-model', configure RADIUS server 'RADIUS_SERVER' with key 'cisco123', and apply 'aaa authentication login default group radius local'.
Why this is correct
This is correct because 'aaa new-model' enables AAA services, the RADIUS server configuration defines the server and key, and the default login authentication list uses RADIUS first with local fallback. Without these, 802.1X cannot authenticate.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Authentication checks who the user is.
✗
Configure 'aaa authentication login default local' and add the RADIUS server with 'radius-server host 192.0.2.10 key cisco123'.
Why it's wrong here
This is incorrect because the authentication list uses only local authentication, not RADIUS first. The RADIUS server is configured but never referenced in the authentication list, so RADIUS is not used.
✗
Enable AAA with 'aaa new-model' and configure 'aaa authentication login default group radius' without local fallback.
Why it's wrong here
This is incorrect because there is no local fallback; if the RADIUS server is unreachable, authentication fails entirely. The requirement specifies local fallback.
✗
Configure 'aaa new-model', then apply 'dot1x system-auth-control' and 'aaa authentication dot1x default group radius'.
Why it's wrong here
This is incorrect because the question asks for default login authentication, not dot1x authentication. The 'aaa authentication login' command is for login (management access), while 'aaa authentication dot1x' is for 802.1X port authentication. The problem is about login authentication, not dot1x authentication list.
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.
✓Enable AAA with 'aaa new-model', configure RADIUS server 'RADIUS_SERVER' with key 'cisco123', and apply 'aaa authentication login default group radius local'.Correct answer▾
Why this is correct
This is correct because 'aaa new-model' enables AAA services, the RADIUS server configuration defines the server and key, and the default login authentication list uses RADIUS first with local fallback. Without these, 802.1X cannot authenticate.
✗Configure 'aaa authentication login default local' and add the RADIUS server with 'radius-server host 192.0.2.10 key cisco123'.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the authentication list must include 'group radius' to use RADIUS; 'local' alone bypasses RADIUS.
Why candidates choose this
Candidates might think that configuring the RADIUS server automatically makes it the default, but the authentication list must explicitly reference it.
✗Enable AAA with 'aaa new-model' and configure 'aaa authentication login default group radius' without local fallback.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is omitting 'local' from the authentication list, which violates the requirement for fallback.
Why candidates choose this
Candidates might overlook the fallback requirement or think that RADIUS alone is sufficient, but the question explicitly asks for local fallback.
✗Configure 'aaa new-model', then apply 'dot1x system-auth-control' and 'aaa authentication dot1x default group radius'.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is confusing 'aaa authentication login' with 'aaa authentication dot1x'. They serve different purposes.
Why candidates choose this
Candidates might associate 802.1X with dot1x authentication and incorrectly apply the dot1x authentication list instead of the login authentication list.
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 question asks for default login authentication, not dot1x authentication. The 'aaa authentication login' command is for login (management access), while 'aaa authentication dot1x' is for 802.1X port authentication. The problem is about login authentication, not dot1x authentication list.
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: Enable AAA with 'aaa new-model', configure RADIUS server 'RADIUS_SERVER' with key 'cisco123', and apply 'aaa authentication login default group radius local'. — The problem is that AAA is not enabled (no aaa new-model) and no RADIUS server is configured; thus the 802.1X authentication fails because the router does not know how to communicate with the RADIUS server. The fix requires enabling AAA with 'aaa new-model', configuring the RADIUS server with 'radius server RADIUS_SERVER' and its key, then applying a default authentication list that uses RADIUS with local fallback via 'aaa authentication login default group radius local'. After these commands, the port should transition to authorized state for valid credentials.
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.
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