mediumMultiple Select
350-401 Practice Question: Which two statements about AAA accounting are…
Which two statements about AAA accounting are true? (Choose two.)
⚠ Common exam trap
350-401 often tests the transport protocol differences between RADIUS (UDP) and TACACS+ (TCP) and the encryption scope (RADIUS encrypts only password, TACACS+ encrypts entire packet), and a common mistake is to assume both use UDP or that TACACS+ only encrypts passwords.
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
✓
RADIUS accounting uses UDP as the transport protocol.
Option A is correct because RADIUS accounting operates over UDP, using destination port 1813 (or the legacy 1646), since RADIUS is a UDP-based protocol for authentication, authorization, and accounting. Option C is correct because the wait-start accounting method requires the accounting start record to be acknowledged by the AAA server before the user is granted access, unlike start-stop which sends the start record without waiting for confirmation. Option B is incorrect because TACACS+ uses TCP (port 49), not UDP, for its accounting traffic. Option D is incorrect because AAA accounting can be applied to EXEC sessions, network access (such as PPP or VPDN), and system-level events, not EXEC sessions alone. Option E is incorrect because TACACS+ encrypts the entire packet body, not just the password portion, which is a characteristic of RADIUS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
RADIUS accounting uses UDP as the transport protocol.
Why this is correct
RADIUS accounting carries its start, stop and interim records over UDP, typically to port 1813, relying on retransmission rather than a connection-oriented session. TACACS+ instead uses TCP, so this UDP transport detail distinguishes RADIUS accounting behaviour in the stated comparison.
- ✗
TACACS+ accounting uses UDP as the transport protocol.
Why it's wrong here
TACACS+ accounting runs over TCP port 49, giving reliable delivery of start, stop and interim records. The option tempts because RADIUS uses UDP for authentication and accounting, so UDP is genuinely associated with AAA accounting — just not with TACACS+.
- ✓
The wait-start accounting method delays service until the accounting start packet is acknowledged by the server.
Why this is correct
Wait-start accounting holds the user's session until the AAA server acknowledges the accounting start record, unlike start-stop, which permits access immediately. This guarantees accounting data is captured before service begins, satisfying scenarios demanding accurate session logging for billing or auditing.
- ✗
AAA accounting is only supported for EXEC sessions, not for network access.
Why it's wrong here
Accounting records both EXEC sessions and network access sessions, such as PPP or VPN user connections, via start, stop and interim records. The option tempts because EXEC accounting is the most commonly configured type, but it is one category rather than the only supported one.
- ✗
TACACS+ encrypts only the password portion of the accounting packet.
Why it's wrong here
TACACS+ encrypts the entire packet body, including username, arguments and accounting attributes, leaving only the header in clear text. The option tempts because RADIUS encrypts just the password field, so that behaviour is real — it simply belongs to RADIUS, not TACACS+.
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
Related to this question
Learn chapter
VLANs and Spanning Tree Protocol Concepts
Key term
802.1X Authentication
802.1X is a network access control protocol that prevents unauthorized devices from connecting to a wired or wireless network by requiring them to authenticate before gaining access.
Key term
RADIUS vs TACACS+
RADIUS and TACACS+ are two network protocols used to verify user identities and control access to network devices and services, with different approaches to security and flexibility.
About these practice questions
This 350-401 question is part of Courseiva's 1,923-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.