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Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
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Chapter 31 Configuring PFC QoS
Configuring PFC QoS
When setting the receive-queue size ratio, note the following:
• The rcv-queue queue-limit command configures ports on a per-ASIC basis.
• Estimate the mix of strict priority-to-standard traffic on your network (for example, 80 percent
standard traffic and 20 percent strict-priority traffic).
• Use the estimated percentages as queue weights.
• Valid values are from 1 to 100 percent, except on 1p1q8t ingress LAN ports, where valid values for
the strict priority queue are from 3 to 100 percent.
This example shows how to set the receive-queue size ratio for Fast Ethernet port 2/2:
Router# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router(config)# interface fastethernet 2/2
Router(config-if)# rcv-queue queue-limit 75 15
Router(config-if)# end
Router#
This example shows how to verify the configuration:
Router# show queueing interface fastethernet 2/2 | include queue-limit
queue-limit ratios: 75[queue 1] 15[queue 2]
Router#
Setting the LAN-Port Transmit-Queue Size Ratio
To set the transmit-queue size ratio on an egress LAN port, perform this task:
When setting the transmit-queue size ratio between transmit queues, note the following:
• Estimate the mix of low priority-to-high priority traffic on your network (for example, 80 percent
low-priority traffic and 20 percent high-priority traffic).
• On LAN ports that have an egress strict priority queue, PFC QoS sets the egress strict-priority queue
size equal to the high-priority queue size.
• Use the estimated percentages as queue weights.
• Valid values are from 1 to 100 percent, except on 1p2q1t egress LAN ports, where valid values for
the high priority queue are from 5 to 100 percent.
Command Purpose
Step 1
Router(config)# interface type
1
slot/port
1. type = ethernet, fastethernet, gigabitethernet, or tengigabitethernet
Selects the interface to configure.
Step 2
Router(config-if)# wrr-queue queue-limit
low_priority_queue_weight
[medium_priority_queue_weight]
high_priority_queue_weight
Sets the transmit-queue size ratio between transmit
queues.
Router(config-if)# no wrr-queue queue-limit
Reverts to the default transmit-queue size ratio.
Step 3
Router(config-if)# end
Exits configuration mode.
Step 4
Router# show queueing interface type
1
slot/port
Verifies the configuration.
