350-601 Security Practice Question
A large financial institution has a Cisco ACI fabric with multiple tenants. The security team requires that all management access to the APIC controllers be authenticated via multi-factor authentication (MFA) using a RADIUS server. The RADIUS server is configured to send a One-Time Password (OTP) challenge during authentication. The current configuration uses local authentication. The engineer needs to implement RADIUS authentication with MFA for APIC GUI and CLI access. The RADIUS server is reachable at 10.10.10.10, shared secret 'SecureSecret123'. The APIC is running software version 4.2(3). The engineer must ensure that local authentication is used as fallback if the RADIUS server is unreachable. Which of the following actions should the engineer take?
⚠ Common exam trap
Cisco often tests the requirement to create a login domain and assign it to users, as many candidates mistakenly think simply adding a RADIUS provider is sufficient without configuring the domain and fallback.
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
✓
Add a RADIUS provider with IP 10.10.10.10 and secret 'SecureSecret123', create a login domain with realm 'radius', set fallback to 'local', and assign the domain to users.
It follows the required steps to configure RADIUS authentication with MFA on Cisco APIC: adding a RADIUS provider with the correct IP and shared secret, creating a login domain with realm 'radius', setting fallback to 'local', and assigning the domain to users. This ensures that the APIC sends authentication requests to the RADIUS server, which can issue an OTP challenge for MFA, and falls back to local authentication if the RADIUS server is unreachable.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure TACACS+ as the authentication protocol and set the server IP and secret.
Why it's wrong here
The requirement is RADIUS, not TACACS+.
- ✗
Enable local authentication only and require strong passwords.
Why it's wrong here
MFA is required; local alone does not provide MFA.
- ✓
Add a RADIUS provider with IP 10.10.10.10 and secret 'SecureSecret123', create a login domain with realm 'radius', set fallback to 'local', and assign the domain to users.
Why this is correct
Correct: RADIUS with PAP is used for MFA and fallback to local.
- ✗
Configure LDAP authentication with the RADIUS server acting as an LDAP proxy.
Why it's wrong here
LDAP is not designed for OTP challenges.
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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