350-001 Question #116: Real Exam Question with Answer & Explanation

Question

Exhibit

Options

• AWRED
• Btraffic shaping
• Cpacket marking
• Dpacket classification
• EFIFO queuing within the class

Explanation

Within a class queue, processing is always FIFO, except for the class-default queue. CBWFQ supports 64 queues, with a maximum and default queue length varying depending on the model of router and the amount of memory installed. All 64 queues can be configured, but one class queue, called class-default, is automatically configured. If the explicitly configured classification does not match a packet, IOS places the packet into the class-default class. Currently, CBWFQ can use either FIFO or WFQ inside the class-default queue. With Flow-Based WFQ in the class-default queue, when CBWFQ decides to take one or more packets from the queue, it takes the packet with the best sequence number (SN) -- just like WFQ normally does. Cisco 7500 series routers support either FIFO or WFQ inside each and every CBWFQ queue, whereas other platforms only support both FIFO and WFQ inside CBWFQ's class-default queue. If the default class is allocated a bandwidth, WFQ cannot be enabled for the traffic within the default class. This is true for all platforms except the 7500(and soon the 7200). Currently (except for the Cisco 7500 router platform) all traffic classes except for the default traffic class support only FIFO queuing within the class. On all platforms, the default traffic class can support either FIFO or WFQ within the class. But if the default traffic class is allocated a minimum bandwidth as shown in the figure, WFQ will not be supported in the default traffic class. The only current exception is for the Cisco 7500 series platforms. In this case, the default traffic class will support only FIFO queuing.

No community discussion yet for this question.