Below you can find SRR fast notes regarding Egress Queuing on Cisco 3560-E & 3750-E.

  • Shaped Round Robin (SRR)
  • SRR – shape mode (srr-queue bandwidth shape)  > BW restriction = policing
  • SRR – share mode (srr-queue bandwidth share) > guaranteed BW based on weight
  • shape overrides share
  • 4 egress queues
  • priority-queue out on an interface, it turns Queue 1 (always Q1) into priority queue
  • WTD – Weighted Tail Drop – queue length
  • queue set 1 is assigned to all ports by default
  • 0 (zero) means that queue works in the shared mode
  • queue can be configured per port basic

To show default queue configuration use below command:
Switch> show mls qos queue-set
Queueset: 1
Queue   :        1       2       3       4
----------------------------------------------
buffers   :      25      25      25      25
threshold1:      100     200     100     100
threshold2:      100     200     100     100
reserved  :      50      50      50      50
maximum   :      400     400     400     400
Queueset: 2
Queue   :        1       2       3       4
----------------------------------------------
buffers   :      25      25      25      25
threshold1:      100     200     100     100
threshold2:      100     200     100     100
reserved  :      50      50      50      50
maximum   :      400     400     400     400

Queue map
To map specific cos or dscp values to Queue 1,2,3 or 4 and to threshold 1 or 2 use below command, example shows that DSCP 16 17 18 19 will be assigned to queue 1 and threshold 1:
mls qos srr-queue output dscp-map queue 1 threshold 1 16 17 18 19
Queue configuration (queue-set) – buffer and threshold
Detail explanation of the Buffer, Memory and Thresholds allocation you can find in this post.
To configure the queue-set buffer percentage use below command:mls qos queue-set output QS-ID buffers Q1% Q2% Q3% Q4%
To configure the queue-set threshold values use below command:mls cos queue-set output QS-ID threshold Q1 DT1 DT2 RT MT

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