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Windows 2019 Network IS SLOW ON HYPER-V 2019

VM 2019 hosted on Hyper-v 2019 can have serious network performance issue . While windows 2008 to Windows 2012 R2 work just fine and fast !

I have found that fine tuning the TCP settings can resolve the issue, in my case it was CUBIC settings.

CUBIC is an implementation of TCP with an optimized congestion control algorithm for high bandwidth networks with high latency (LFN: long fat networks). CUBIC TCP is implemented and used by default in Linux kernels 2.6. 19 and above, as well as Windows 10.1709 Fall Creators Update, and Windows Server 2016 1709 update

Try to change the setting to CTCP Short for client-to-client protocol :

(run as administrator)

netsh int tcp set supplemental template=internet congestionprovider=CTCP
netsh int tcp set supplemental template=internetcustom congestionprovider=CTCP
netsh int tcp set supplemental template=Datacenter congestionprovider=DCTCP
netsh int tcp set supplemental template=Datacentercustom congestionprovider=DCTCP

To change Back to CUBIC

netsh int tcp set supplemental template=internet congestionprovider=CUBIC
netsh int tcp set supplemental template=internetcustom congestionprovider=CUBIC
netsh int tcp set supplemental template=Datacenter congestionprovider=CUBIC
netsh int tcp set supplemental template=Datacentercustom congestionprovider=CUBIC

Good Luck

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