mediumMultiple Choice
350-401 Practice Question: Consider this AAA configuration: aaa new-model…
Consider this AAA configuration:
aaa new-model aaa authentication login default local aaa authorization exec default local aaa accounting exec default start-stop group tacacs+
tacacs-server host 10.0.0.1 key SecretKey
line con 0
login authentication default
line vty 0 4
login authentication default
What is the effect of this configuration?
⚠ Common exam trap
Cisco often tests the distinction between authentication, authorization, and accounting method lists, and the trap here is that candidates assume 'default' in the accounting command implies local accounting, when in fact it refers to the method list name and the actual method is specified by 'group tacacs+'.
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
✓
All login attempts use local authentication; exec accounting is sent to TACACS+.
The configuration sets AAA authentication login to use the local user database (via 'aaa authentication login default local'), so all login attempts (console and VTY) authenticate against the local device. Authorization for exec sessions is also set to local ('aaa authorization exec default local'), meaning no external authorization is used. Accounting for exec sessions is configured with 'start-stop' and points to the TACACS+ server at 10.0.0.1, so all exec session start and stop records are sent to TACACS+. This matches option A.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
All login attempts use local authentication; exec accounting is sent to TACACS+.
Why this is correct
The command `aaa authentication login default local` applies local authentication to every login attempt, regardless of transport (console, VTY, or auxiliary). Additionally, `aaa authorization exec default local` defers authorization decisions to the local database, but that is not contradicted here. The final command, `aaa accounting exec default start-stop group tacacs+`, instructs the device to generate start and stop accounting records for each EXEC session and forward them to the TACACS+ server. Thus, authentication is local, while accounting is sent remotely to TACACS+.
- ✗
All login attempts use TACACS+ authentication; exec accounting is local.
Why it's wrong here
This option reverses both authentication and accounting elements from the actual configuration. The `aaa authentication login default local` command explicitly selects the local username/password database as the method, not TACACS+; no TACACS+ group is referenced in the authentication method list. Similarly, the accounting command `aaa accounting exec default start-stop group tacacs+` sends EXEC accounting data to the TACACS+ server, not to local accounting logs. Therefore, this statement is incorrect on both counts.
- ✗
Console login uses TACACS+; VTY login uses local; accounting is sent to TACACS+.
Why it's wrong here
It presupposes separate authentication method lists for console and VTY. In the given configuration, only a single default method list is defined under `aaa authentication login default local`, and both console and VTY automatically reference this same default list. Therefore, all login transports, including console and VTY, authenticate against the local username database. The accounting part is accurate—`aaa accounting exec default start-stop group tacacs+` sends EXEC start and stop records to TACACS+—but the authentication split is unsupported by the config.
- ✗
Authentication and authorization are both performed by TACACS+; accounting is local.
Why it's wrong here
This option is the inverse of the correct behavior: authentication and authorization are both local, while accounting is remote. The absence of `group tacacs+` in the `aaa authentication login default` and `aaa authorization exec default` lines confirms that the router consults its local username database for both functions. In contrast, `aaa accounting exec default start-stop group tacacs+` designates TACACS+ as the sole accounting destination. Because the three AAA sub-services are configured independently, using TACACS+ only for accounting is perfectly valid and does not imply it is used for the other two.
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.
Go deeper
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Key term
AAA on Cisco Devices
AAA on Cisco devices is a security framework that controls who can access the network, what they can do, and keeps a record of their actions.
Key term
Cisco ISE
Cisco Identity Services Engine is a security policy management platform that controls who can access a network and what they can do once connected.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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