02-23-2021 03:03 PM
Hello, I have worked for years somewhere QoS wasn't used, and now I have to relearn it.
Firtst, RTFM, then I'm doing a small lab with 2 identical 2960 (LAN Lite, 8 ports) with a single trunk to try it out.
I was trying to make vlan 4 behave as "best effort" and vlan 2 have priority on the trunk. I was hoping to force CoS 5 on vlan 2 traffic then expedite egress queue 1 on the trunk interface.
That didn't work, traffic from SwitchA vlan 4 to SwitchB vlan 4 (going through the trunk fa0/8) can saturate the trunk at 100Mbps, but SwitchA vlan 2 to SwitchB vlan 2 has it's bandwith limited to 4Mbps whether the trunk is saturated or not.
I am clearly missiong something, but I have read the full doccument, can anyone find a clue with the folloing info? Thank you.
Drawing: Host1--(fa0/6)-SwitchA-(trunk-fa0/8)-SwitchB--(fa0/6)-Host3
Host2--(fa0/7)----| |----(fa0/7)-Host4
Both SwitchA and SwitchB have identical configs:
mls qos ! interface FastEthernet0/6 switchport access vlan 4 switchport mode access ! interface FastEthernet0/7 switchport access vlan 2 switchport mode access mls qos cos 5 mls qos cos override ! interface FastEthernet0/8 switchport mode trunk priority-queue out mls qos trust cos !
Show:
#show mls qos input-queue Queue : 1 2 ---------------------------------------------- buffers : 90 10 bandwidth : 4 4 priority : 0 10 threshold1: 100 100 threshold2: 100 100 #show mls qos maps Cos-outputq-threshold map: cos: 0 1 2 3 4 5 6 7 ------------------------------------ queue-threshold: 2-1 2-1 3-1 3-1 4-1 1-1 4-1 4-1 Cos-inputq-threshold map: cos: 0 1 2 3 4 5 6 7 ------------------------------------ queue-threshold: 1-1 1-1 1-1 1-1 1-1 2-1 1-1 1-1 #show mls qos interface FastEthernet0/6 trust state: not trusted trust mode: not trusted trust enabled flag: ena COS override: dis default COS: 0 FastEthernet0/7 trust state: cos override trust mode: cos override trust enabled flag: ena COS override: ena default COS: 5 FastEthernet0/8 trust state: trust cos trust mode: trust cos trust enabled flag: ena COS override: dis default COS: 0 #show mls qos interface queueing FastEthernet0/6 Egress Priority Queue : disabled Shaped queue weights (absolute) : 25 0 0 0 Shared queue weights : 25 25 25 25 The port bandwidth limit : 100 (Operational Bandwidth:100.0) The port is mapped to qset : 1 FastEthernet0/7 Egress Priority Queue : disabled Shaped queue weights (absolute) : 25 0 0 0 Shared queue weights : 25 25 25 25 The port bandwidth limit : 100 (Operational Bandwidth:100.0) The port is mapped to qset : 1 FastEthernet0/8 Egress Priority Queue : enabled Shaped queue weights (absolute) : 25 0 0 0 Shared queue weights : 25 25 25 25 The port bandwidth limit : 100 (Operational Bandwidth:100.0) The port is mapped to qset : 1
02-24-2021 07:00 AM
From what you're describing, it sounds like the default shaper is active on f0/8's Q1, although I believe PQ activation should override that. However, if your IOS is an old version, it might be a bug or the fact you note it's a "Lite" 2960, which, I also believe, is lacking some QoS features.
What you might try is:
srr-queue bandwidth shape 0 0 0 0
On interface f0/8.
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