300-320 Question #624: Real Exam Question with Answer & Explanation

The correct answer is C: it is shared by other classes.. In Cisco CBWFQ (Class-Based Weighted Fair Queuing), the bandwidth value assigned to a class defines a minimum guaranteed allocation, not a hard ceiling. When a class is not actively generating enough traffic to consume its full allocation - for example, during periods of silence

Question

Refer to the exhibit. The voice class uses 200 Mb of bandwidth and the signaling class uses 50 Mb of bandwidth. What happens to the unused bandwidth?

Exhibit

Options

AIt is reserved for the signaling class.
BIt is used by the video class.
Cit is shared by other classes.
Dit is reserved for the voice class.

Explanation

In Cisco CBWFQ (Class-Based Weighted Fair Queuing), the bandwidth value assigned to a class defines a minimum guaranteed allocation, not a hard ceiling. When a class is not actively generating enough traffic to consume its full allocation - for example, during periods of silence in the voice class or low signaling activity - the unused bandwidth does not sit idle or get reserved for that class. Instead, it becomes available to all other active classes, distributed proportionally based on their relative bandwidth weights. This dynamic sharing ensures efficient link utilization. The voice and signaling guarantees are preserved under congestion, but surplus capacity is always redistributed across all competing traffic classes.

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