350-401 · Question #69
Which statement about the default QoS configuration on a Cisco switch is true?
The correct answer is C. The Port Cos value is 0.. This question examines the default Quality of Service (QoS) configuration on Cisco switches.
Question
Which statement about the default QoS configuration on a Cisco switch is true?
Options
- AAll traffic is sent through four egress queues.
- BPort trust is enabled.
- CThe Port Cos value is 0.
- DThe Cos value of each tagged packet is modified.
How the community answered
(38 responses)- A5% (2)
- B3% (1)
- C89% (34)
- D3% (1)
Why each option
This question examines the default Quality of Service (QoS) configuration on Cisco switches.
The number of egress queues can vary significantly by Cisco switch model and software version; four queues are not a universal default for all traffic on all switches.
Port trust is generally disabled by default on Cisco switch ports, meaning the switch does not honor incoming QoS markings (CoS or DSCP).
By default, Cisco switch ports are untrusted for QoS, meaning they assign a default internal Class of Service (CoS) value of 0 to incoming traffic, regardless of any CoS value present in the frame.
The CoS value of tagged packets is not modified by default on untrusted ports; rather, the switch reclassifies the traffic internally based on the default CoS 0, but the original CoS in the frame is preserved unless explicitly re-marked.
Concept tested: Default Cisco switch QoS configuration
Source: https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/16-12/configuration_guide/qos/b_1612_qos_9300_cg/configuring_qos.html
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