Cisco Quality of Service (QoS) - 642-642 Exam Questions [2026]

QUESTION NO: 1
At the network layer, IP packets are typically classified based on which three items? (Choose three.)

A. content of the ToS byte B. VLAN Identifier C. packet length D. source and destination IP addresses E. flow control bits

Correct Answer: A,C,D

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).

QUESTION NO: 2
When configuring a Cisco Catalyst switch to accommodate an IP phone with an attached PC, it is desired that the trust boundary be set between the IP phone and the switch. Which two commands on the switch are recommended to set the trust boundary as described? (Choose two.)

A. mls qos cos 5 B. mls qos trust cos C. switchport priority extend trust D. no mls qos trust dscp E. mls qos trust extend [cos value] F. mls qos trust device cisco-phone

Correct Answer: B,F

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).

QUESTION NO: 3
QoS policy propagation through BGP (QPPB) supports which two QoS markers? (Choose two.)

A. MPLS EXP B. COS C. DSCP D. QoS group E. IP precedence

Correct Answer: D,E

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).

QUESTION NO: 4
In a managed CE scenario, the customer's network is supporting VoIP and bulk file transfers. According to the best practices, which QoS mechanisms should be applied on the WAN edge CEPE 56-kbps Frame Relay link on the CE outbound direction?

A. WRR, FRTS, FRF.12, and CB-RTP header compression B. CBWFQ, CB-WRED, CB-Marking, CB-Policing, and FRTS C. CBWFQ, FRTS, FRF.12, and CB-RTP header compression D. WRR, CB-WRED, CB-Marking, FRF.12, and CB-RTP header compression E. LLQ, CB-WRED, CB-Marking, FRTS, FRF.12, and CB-RTP header compression F. LLQ, CB-WRED, CB-Policing, and CB-TCP and CB-RTP header compressions

Correct Answer: E

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).

QUESTION NO: 5
SIMULATION - LAB

A. Please click console

Correct Answer: A

R1>en
R1#configure terminal
R1(config)#policy-map llq-policy
R1(config-pmap)#class voice
R1(config-pmap-c)#prority 168
R1(config-pmap-c)#exit
R1(config-pmap)#class interactive
R1(config-pmap-c)#prority 30
R1(config-pmap-c)#exit
R1(config-pmap)#class bulk
R1(config-pmap-c)#prority 16
R1(config-pmap-c)#exit
R1(config-pmap)#class class-default
R1(config-pmap-c)#fair-queue
R1(config-pmap-c)#exit
R1(config-pmap)#exit
R1(config)#int s0/0
R1(config-if)#service-policy output llq-policy

QUESTION NO: 6
HOTSPOT

Correct Answer:

QUESTION NO: 7
Which of the following configurations requires the use of hierarchical policy maps?

A. the use of both the bandwidth and shape statements within a CBWFQ class queue B. the use of class-based WRED within a CBWFQ class queue C. the use of CBWFQ inside class-based shaping D. the use of nested class-maps with class-based marking E. the use of a strict priority-class queue within CBWFQ

Correct Answer: C

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).

QUESTION NO: 8
Which element is mandatory for QoS policy propagation through BGP operations?

A. MPLS B. QoS pre-classify C. NBAR D. policy-based routing E. CEF F. MQC

Correct Answer: E

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).

QUESTION NO: 9
Refer to the exhibit. A typical configuration involving an IP phone with an attached PC is shown. According to QoS recommendations, at which demarcation line (shown as dotted lines) would the trust boundary normally exist?

A. D B. B C. C D. A

Correct Answer: B

Explanation: Only visible for Pass4Test members. You can sign-up / login (it's free).