350-601 Security Practice Question
An engineer is configuring AAA authentication on a Cisco MDS 9000 series switch. The goal is to authenticate users via RADIUS first, then local as a fallback. Which command sequence should be used?
⚠ Common exam trap
Cisco often tests the distinction between 'default' (applies to all login methods) and specific method names like 'console' or 'ssh', and the requirement to use the 'group' keyword before the server group name, causing candidates to omit 'group' or choose a method-specific keyword incorrectly.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
aaa authentication login default group radius local
The 'aaa authentication login default group radius local' command configures the switch to first attempt RADIUS authentication for all login methods (default), and if the RADIUS server is unreachable or returns an error (not a rejection), it falls back to the local user database. This matches the requirement of RADIUS first with local fallback.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
aaa authentication login default group radius local
Why this is correct
Correct syntax: 'default' login method, 'group' keyword, radius then local fallback.
- ✗
aaa authentication login default local radius
Why it's wrong here
Order is reversed; local would be tried first.
- ✗
aaa authentication login default radius local
Why it's wrong here
Missing the 'group' keyword; incorrect syntax for MDS.
- ✗
aaa authentication login console radius local
Why it's wrong here
Uses 'console' instead of 'default'; should apply to all login methods.
Quick reference
AAA Protocol Comparison
| Protocol | Port(s) | Encryption | Transport | Primary Use |
|---|---|---|---|---|
| RADIUS | 1812 / 1813 | Password only | UDP | Network access control |
| TACACS+ | 49 | Full packet | TCP | Device administration |
| Diameter | 3868 | Full session | TCP / SCTP | Carrier / mobile networks |
| 802.1X | — | EAP-based | Layer 2 | Port-based access control |
TACACS+ encrypts the entire packet; RADIUS only encrypts the password field — a key exam distinction.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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