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