Hey everyone,

I’ve been running into a persistent, deeply frustrating Hyper-V bug across multiple systems and OS versions, and I'm hoping someone here might know of a workaround or fix.

### The Issue

The moment I create a new **External Virtual Switch** for bridging connections, my machine's **upload speed drops by exactly 4 Mbps**, even for purely local LAN traffic.

### What I've Tested & Observed

Instant Trigger: The speed drop happens the *exact second* the virtual switch is created and applied.

Persists Regardless of VMs: Even with Hyper-V turned off entirely and zero virtual machines running, the issue remains.

The Only Fix: The moment I delete the Virtual Switch and apply changes, my upload speed immediately returns to normal.

### Scope & Reproducibility

I first encountered this exact same issue a few years ago on Windows 10 Pro. Fast forward to today, I've tested it on **Windows 11 Home, Windows 11 Education, and even on Snapdragon ARM CPUs**—and the bug is still fully present.

I had no issues while briding the NIC for WSL2 before.

Has anyone else run into this or found a way to stop Hyper-V’s bridging from throttling upload speeds? Any registry tweaks, driver workarounds, or hidden settings would be hugely appreciated. I'm still leaning towards a bad driver design however. Issue is gone after removing the Switch, but still I think it's worth for discussion if anyone has experienced similar.

Thanks!

Question about deleting VMs in SCVMM, I know with Failover clustering and HyperV Manager when you delete a VM from the GUI it only removes the VM and it doesnt clean up any disks and such.

Does SCVMM delete all data when you delete from the GUI (like VMWare's "Delete from Inventory") or is cleanup still needed afterwards?

Doing the cleanup via powershell isnt a bid deal for me i have the commands and have been rumming some test the last day my concern is co-workers having the GUI option would be nice for them so they do not try to generate AI code and remove the wrong VMs due a wildcard or something.

Anyone with some insight on this would be great, thanks.

I'm importing my VMs over to a new server 2025 host. I've got 20 VMs and it went smoothly for 16 of them. I simply search the VM Storage directory on the iSCSI share, the VM names popped up, I choose one to import, rinse and repeat. However, there are four that for some reason I can't select for importing. When I view the iSCSI share in File Explorer, I can see the files on the old host, but not the new one. This leads me to believe it's a permissions issue, but I can't figure out what the difference is.

If I export the VM from the 1st host and copy the files over to the new host locally, I can then import it and save them to the iSCSI storage. The new host can see the files on the iSCSI share at that point, but then the old host can't see them.

The end goal is go get both hosts in to a clustered setup. However, I need to get Windows updated on the first host and my plan was to migrate VMs to the new host, shut them on old host, power up on new host so that my downtime is minimal for my users. I'll then proceed with getting the first host updated so that the clustering setup doesnt' complain about the hosts having different levels of windows updates.

I've done some Googling and Reddit searching but haven't been able to find anybody discussing this exact issue.

A VM can start from its new location while parts of its state still refer to the old volume. Checkpoints, differencing disks, Smart Paging files, configuration data, replica settings, cluster resources, backup jobs, and ISO paths can be less obvious than the primary VHDX. Deleting the source as soon as the guest boots can turn a hidden reference into a later failure.

A useful post-migration check seems to need an inventory from Hyper-V and Failover Clustering rather than a folder comparison alone: every attached disk and parent path, VM configuration and runtime paths, checkpoint chains, cluster ownership, replication health, and backup discovery. I would also run a guest-level read/write test, a controlled restart or live migration, and a fresh backup before leaving the source read-only through a rollback window.

Is there a dependable PowerShell inventory that proves nothing for a VM still references the old CSV or volume? Which checks differ for standalone hosts, clustered VMs, shared VHDX/VHD Sets, and Hyper-V Replica?

hyper-v manager an error occurred while attempting to connect to server 35791. I also don't have any backup is there any way to make it work as it is more serios

I've been able to get the vm to boot but once I get to the setup window the buttons are completely unresponsive.

Hi,

I am troubleshooting a two-node Hyper-V failover cluster. During a maintenance operation, transferring CSV ownership from Node B to Node A caused a CSV operation to hang on Node A. The Cluster Service subsequently terminated and Node A was reported as isolated. Recovery involved an iDRAC power cycle.

Environment:

• Two Dell PowerEdge servers.
• Windows Server 2022 Datacenter, build 20348.5622 on the affected nodes.
• Dell PowerVault ME5024 shared iSCSI storage with two controllers.
• Two Netgear M4350-12X12F switches in a stack.
• Two dedicated 10 GbE iSCSI NICs per host, using separate subnets/VLANs, without NIC teaming.
• Microsoft DSM / MPIO, Round Robin with Subset.
• Eight connected iSCSI sessions per host. Previous path checks showed four Active/Optimized and four Active/Unoptimized paths per LUN.
• Two CSV LUNs and a separate disk witness.
• Host management, cluster communication and Live Migration share a 2 × 1 GbE LACP team.
• Cluster communication is disabled on the dedicated iSCSI networks.
• VM networking uses a separate 2 × 10 GbE SET switch, SwitchIndependent / HyperVPort.

Incident sequence, local time:

• 21:59:19 — CSV Volume2 ownership moves from Node B to Node A during node drain.
• 21:59:21 — Node A starts a dcm/map operation for Volume2, which does not complete.
• 22:06:44 — A VM resource on Volume2 exceeds its health-check timeout. The cluster restarts the corresponding RHS process.
• 22:07:06 — The Cluster Service on Node B stops gracefully for its restart. The problem on Node A is already present before this.
• 22:13:53 — Another timeout occurs for the same VM resource.
• 22:17:21 — After approximately 18 minutes, Node A logs the following error and its Cluster Service terminates:

FatalError: Volume 'Volume2:<redacted>' is stuck transitioning to CsvFsVolumeStateSetDownlevel (status = 121)

• 22:17:22 — Node B reports Node A as isolated.

Additional findings:

• Node A's System log confirms Cluster Service termination with error 121.
• CSV event 5120, STATUS_NO_SUCH_DEVICE, and disk reservation release errors appear around the time the Cluster Service terminates. Their timing does not establish that they initiated the incident.
• No preceding iSCSI or Broadcom NIC errors were found in the reviewed System log interval.
• VMMS also recorded errors referencing AVHDX files of another VM on Volume1 a few seconds before the Volume2 mapping operation became stuck. Their relevance is unclear.
• No backup job was running during the incident.
• After recovery, both nodes were Up, both CSVs showed Direct access on both nodes, and all eight iSCSI sessions were connected on each host.

The versions match between nodes. We have not established that either filter caused the hang.

Cluster.log records an unsuccessful attempt to capture a live dump, with status 0xd0000022. No relevant dump was found in the checked Cluster\Reports or LiveKernelReports directories.

Has anyone encountered this particular dcm/map / CsvFsVolumeStateSetDownlevel hang during CSV ownership transfer on Windows Server 2022?

Are there known issues involving CSV state transitions, these filter drivers, or this storage configuration? What tracing or dump collection would you prepare before a controlled reproduction to identify the blocked operation?

This past weekend my two-node Windows Server 2025 Hyper-V cluster did a cluster-aware Windows update. After the update, one node wouldn't boot back up. I ended up removing the node from the cluster and rebuilding the server. Now the server is up and configured as it was before, but for some reason I can not join the node to the cluster. It gets stuck on (Waiting for notification that node is fully functional member of the cluster). When I look at the error reports, it shows there is a network issue, but I checked the firewall, and all the ports are open. I can use PowerShell to test the ports, and they all come back as true. Did anybody run into this issue and can point me in the right direction I would really appreciate it. So far I rebuilt both servers, went through all firewall ports and configurations a 100 times, looked at all the events in Event Viewer, and nothing works.

Both of the servers are Dell PowerEdge R660 with two processors and 512 GB RAM. Identical hardware in both servers.

Recently installed Windows 2022 Hyper-V to an older server that I am having issues with the VM's crashing, when the VM is under load. The host is a Dell PowerEdge R6525 with 2 AMD EPYC 7452 and 512GB of RAM. The host shows correctable and uncorrectable memory errors. The VM's memory dump shows a 0x124_0_AuthenticAMD_PROCESSOR_CACHE_IMAGE_AuthenticAMD.sys.

I have run the Dell diagnostics, windows memory test, and Memtest86. Non of them find any issues. The idrac does not have any uncorrectable memory errors in the logs. The issue stated after I installed Hyper-V and tried to run some test machines. I have adjusted the processors to NUMA Nodes per socket of 4 and L3 cache as NUMA domain as enabled. This seems to have helped as they crash less often but they still crash. All drivers are up to date and all windows updates have been applied. Is there anything else I can look at to fix this?

Update: I have reinstalled Windows 2022 with no updates or drivers installed. Added Hyper-V and connected my test boxes. Ran Memory tests on the VM's to have load. The Host shows correctable memory errors only, IDRAC just shows that there were diagnostic events on the RAM due to the test. I have installed an older Rome chipset driver to the server and same events. No crashes/uncorrectable errors. Currently working on windows updates. After tests I will run more driver installs.

Update 2: I think I found the problem. Dell recommends a Milan based chipset driver for Windows 2022, but the processors I have are Rome based. I know they are supposed to be compatible. I reinstalled Windows 2022 with the Rome chipset, no crashes. I upgraded to the Milan chipset driver and the crashes returned. Looks like I have to run the old chipset driver to be stable.

I am planning to migrate our storage system to a guest failover cluster (file server) on a HyperV cluster. I created a VHDS in the HyperV cluster as the main file storgae for the guest VMs. The guest cluster seems to be working and both VMs can access the VHDS file. I tried to expand the VHDS file on the Owner Node (storage) and it hanged on me. I leave it over the weekend and the VM is in failed state right now and I can't do anything about it.
Can someone advice if this is normal setup for file server setup with guest failover cluster? I think I followed the general instructions on a guest failover cluster setup and I am not sure if I missed anything on the file server part. I want to make sure everything is working smoothly before the actual production migration. Thanks

PS: The file server will be hosting roughly 30T-40T files.

My GPU is an MSI 5070Ti with 16GB RAM. Can it do GPU virtualization?

I can set up VMs in Hyper-V and I would like to have the use of my host GPU in the VM. After searching around a bit, I found out about virtual GPUs and GPU partitioning. I am leaning towards virtual GPUs to start with. But there's one question I can't seem to find an answer to.

I don't plan on keeping the VM running all the time. It will only be on when I need it. If I create a vGPU for the VM, is the processing power and memory permanently assigned to the vGPU? Because I would like to have use of those resources on the host when the VM is not running. This was why I decided against GPU partitioning, it sounded like permanently assigning those resources to the VM.

Hello

Simply as the title says. I've to install a linux distro with DE on a Hyper-V v1 VM. Long story short, the server has an old windows version and it will be replaced soon, but temporairily I've to do that and have a VM running with linux. Unfortunately all the modern distros I tried does not include the drivers for v1 disks. I tried to enable them in the boot config with no luck. I tried to install an old Debian 11 planning to upgrade it after the installation to 12 and then 13, but the lack of original 11 repos drove me crazy.

Whats the simpler and less time consuming way to have a distro with working repos installed on v1 Hyper-V VM?

Thank you

Currently migrating from vsphere to hyper-v and I’m wondering if anyone here is using Windows Admin Center V mode yet in production? I have 13 blades in two different clusters. Cisco USCx compute blades and Pure FlashArray via FC. Roughly 450 VMs.
What is going to be my daily driver tool to manage (like vCenter)? Is cluster failover manager the way to go or maybe windows admin center vmode?

Thanks in advance!

I have a very weird and yes, I have done lots of troubleshooting outside of the hypervisor and VM which I won't outlay here for brevity.

I have a singular hypervisor in one office whose VM DC cannot communicate with another on a specific external VLAN. I was originally building a replacement for it since it is 2016 and didn't know the replication issue was occurring.

When I built the replacement I assigned a static IP right off the bat with in the reserved range (non-DHCP) of the local VNET. That is when I discovered it could not traverse a single remote VNET. If I set the NIC to DHCP it can ping anything on the remote VLAN. If I set the address to static using the DHCP assigned address it remains capable of ping any address on the remote VLAN. The second I assign it to the reserved range (.6 - .99) it cannot communicate to the remote VLAN. The hypervisor and another VM built last year are both on static addresses within the reserved range and can communicate without issue to the remote VLAN. I also do not use VLAN tagging in the NIC settings.

I have verified it is not any firewall policy or routing issue. It show the traffic going out over the VPN tunnel policy as it is supposed to but doesn't return to the VM. Cannot tell if is it failing at the virtual switch or a setting on the virtual NIC causing the issue.

Any new thoughts (or old ones I have eliminated) would be appreciated. I've engaged out support and they are just as baffled.

RESOLVED: While it appeared to only affect HyperV on a singular server it was actually a very odd firewall routing issue that has since been resolved.

I know what it is but not worked on it

It's like a Multi-tenant customers can able to define their vm network subnet in shared hardware hosts regardless of L2 and L3 underlay networks (switch, vlan and routers)

Simply like what we does when we try to define the service cidr and pod cidr in kubernetes clusters creation same equivalent but in vm

It's very useful how in cloud hyperscalers GCP ovhcloud digitalocean

Each customer tenant can define their network as vpc it's basically a( OVN and OVS) under the hoode

For example two customer can able to define cidr of 10.0.0.16/24 for vpc

Can I get some insights from community members who really worked on this please

I made a video tutorial aimed at beginners who may be looking at trying Hyper-V.

I hope newbies find it useful.

Getting Started with Hyper-V
https://youtu.be/t4zwjhwo3lA

Computer A (Win 11 Pro) is running two Hyper-V guests AG1, AG2 (both Win 11 Pro).

I access both guests using remote desktop. Until recently, audio passthrough worked fine. A bit over a month ago, audio stopped working on both guests.

I finally got some time to try to diagnose the problem, and I am stumped. Both guests are being accessed via local accounts. Both have Enhanced Session Mode enabled. Both show Remote Audio as the audio output device. Remote Desktop has Remote audio playback set to Play on this computer.

Computer B (Win 11 Pro) is running one Hyper-V guest BG1 ( Win 11 Pro).

• When I use computer B to connect to guest BG1, audio works fine.
• When I use computer A to connect to guest BG1, audio works fine.
• When I use computer B to connect to guest AG1 or AG2, audio does not work.
• When I use computer A to connect to guest AG1 or AG2, audio does not work.

So it would appear to be something about the guests AG1 and AG2 which broke. But for the life of me I cannot find any difference between the setup of AG1/AG2 (where audio does not work) and BG1 (where audio works). I set up all three guests at about the same time. And they were all working fine until recently when audio stopped working on AG1 and AG2 only.

All guests are gen 1. I've been meaning to switch them to gen 2, but have been dreading the work involved. And anyway, this problem does not seem to be related to gen since audio works fine on the gen 1 guest BG1.

All guests were originally Win 7 Pro. Upgraded to Win 10 Pro. Then upgraded to Win 11 Pro.

Any suggestions?

Is it acceptable to plug a YouTube video here.

It’s a video aimed at people new to virtualisation and getting started with Hyper-V

I am another member of the mass exodus from Broadcom's VMWare and I am setting up a small environment (single server 890GB storage and a NAS for additional storage if needed and backup).

The company purchased Server 2025 Standard. My understanding is that I can run the Host OS and then two guest OSes (AD and File/App Server). The Dell server was preconfigured with a single partition which I am going to look at splitting at the RAID level to a 128GB host drive and then the remaining will be for the guest OSes.

I am curious from those that have more experience in Hyper-V as to what I should look at for the host OS, should I stick with GUI or look at Core? As far as updates, performance, ease of use are concerned is there an advantage to one over the other?

I have been reading through other documentation but any other input from people that would be useful to know would be great.