350-501 Automation and Quality of Services Practice Question
Which TWO statements correctly describe the DiffServ model? (Choose two.)
⚠ Common exam trap
Cisco often tests the distinction between DSCP (6-bit) and IP Precedence (3-bit), and the specific DSCP value for EF (46) versus Best Effort (0), to catch candidates who confuse the bit length or default markings.
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
✓
DSCP uses 6 bits, providing 64 possible values
The DiffServ model uses the 6-bit Differentiated Services Code Point (DSCP) field in the IP header to mark packets, providing 2^6 = 64 possible values (0-63). This allows for up to 64 distinct per-hop behaviors (PHBs), enabling scalable QoS classification beyond the limited 8 classes of the older IP Precedence model.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
AF classes use DSCP values 0-7
Why it's wrong here
Incorrect; AF uses values 8-63.
- ✓
DSCP uses 6 bits, providing 64 possible values
Why this is correct
Correct; DSCP is 6 bits.
- ✗
Best Effort is marked with DSCP 46
Why it's wrong here
Incorrect; BE is DSCP 0.
- ✓
Expedited Forwarding (EF) is defined as DSCP 46
Why this is correct
Correct; EF is DSCP 46.
- ✗
DiffServ uses a 3-bit field for QoS marking
Why it's wrong here
Incorrect; that is for IP precedence.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.