ONT – Cong. Mgnt & Queu. Pt. 2
Describe how Class-Based Weighted Fair Queuing differs from other queuing disciplines like PQ, CQ, and WFQ.
CBWFQ allows the creation of user-defined classes, each of which is assigned to its own queue. Each queue receives a user-defined (minimum) bandwidth guarantee, but it can use more bandwidth if it’s available.
How many queues can be created when using Class-Based Weighted Fair Queuing (CBWFQ)?
CBWFQ can create up to 64 queues, one for each user-defined class, plus a queue called ;class-default;. Each queue is a FIFO queue (and the class-default can be changed to WGQ) with a defined bandwidth guarantee and a maximum packet limit. You can also apply WRED to any queue, including the class-default.
How is the weight of each CBWFQ queue calculated?
The weight is computed by the IOS based on the value you enter for bandwidth, bandwidth percent, or bandwidth remaining percent on the class that is assigned to the queue.

What command is used to allocate a certain amount of bandwidth (Kbps) to the queue of a class?
bandwidth kilobits
What is the maximum reserved bandwidth of an interface when using CBWFQ?
The default is equal to 75 percent of the total bandwidth of that interface.
What command is used to modify the maximum reserved bandwidth on an interface?
max-reserved-bandwidth percent
What command is used to allocate/reserve an amount of bandwidth equal to a certain percent of the interface bandwidth, to the queue of a class?
bandwidth percent percent
What command; is used to allocate a certain percentage of the remaining available bandwidth of an interface to the queue of a class?
bandwidth remaining percent percent
What happens when you use the bandwidth command and the bandwidth percent command in the same policy map?
When you configure the reserved bandwidth for each traffic class in a policy map, you cannot use the bandwidth command for one class and the bandwidth percent command on another class.
What command is used to define a class map?
class-map map-name
What command is used to define a policy map?
policy-map map-name
What policy map statement sets the guaranteed bandwidth for a specific queue?
bandwidth Kbps
What policy map statement sets the maximum packet limit (queue limit) for a specified queue?
queue-limit packets
What policy map statement sets a specific queue from FIFO to WGQ and sets the maximum number of dynamic queues?
fair-queue max-queues
What command displays information about the policy map applied to an interface?
show policy-map interface
How does Low-Latency Queuing (LLQ) differ from other queuing disciplinces?
LLQ includes a strict-priority queue that is given priority over other queues. The priority queue has a minimum bandwidth guarantee, but at the time of congestion, it cannot transmit more data than its bandwidth permits. If the queue is maxed, the excess bandwidth is dropped.

This way, the other queues are not starved.

How does the configuration of LLQ differ from that of CBWFQ?
The configuration of the 2 are almost identical, except for that thestrict-priority queue(s), instead of using the command bandwidth, you use the command priority, within the desired class of the policy map.
What command specifies the bandwidth to be allocated to the strict-priority queue of LLQ?
priority bandwidth {burst}
What command defines the percent of bandwidth that a strict-priority queue will be allocated?
priority percent percentage {burst}