Azure VFP Switch Extension differs between SKUs

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#608 opened on Aug 5, 2025 19 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty: 5/5
Estimated time: Over a week
Newbie friendliness: 28/100

Issue type: Feature
Clarity: Mostly clear
Activity status: Quiet
Tech stack: kubernetes
Domain: devops, networking, operating-systems

Research direction

Reproduce the difference between Windows Server 2025 and Windows 11, then compare the vfpctrl port rules and registry switch-extension entries shown in the issue. Trace the sources of vfpfilter.ini and vfpext.inf to determine whether a forwarding extension can be supported on client SKUs. Done means a supported way to run Calico and Kubernetes workloads with working pod connectivity on Windows 11.

Written by the indexing model from the issue text.

Description

enhancement

Is your feature request related to a problem? Please describe.
I am attempting to run Calico on Windows 11 machines and I'm running into an issue where network connectivity works for pods on Windows Server 2025 but not Windows 11. Having inspected the virtual switch state via vfpctrl, the only real difference seems to be that it is installed as a filtering extension instead of a forwarding extension on client SKUs.

The Switch extension in the registry indicates different INFs and names, even for the same GUID:

(Server 2025)

(Windows 11)

Now I'm not certain this is the root cause, but everything else seems to be identical. On the Windows 11 machine, vfpctrl reports that the rules/layers of the port are dropping packets due to "no match" and I suspect that the filtering extension is lacking some functionality that Calico expects to have working. Forwarding extensions seem to be able to do a lot more, so this is my best guess as to the root cause.

Describe the solution you'd like
Please provide a way for the VFP extension to be switched from "filtering" to "forwarding" mode on client SKUs, so that we can use Kubernetes to orchestrate build/test jobs.

Describe alternatives you've considered
I'm currently trying to track down the source of vfpfilter.ini and vfpext.inf to see if it's possible to directly install the forwarding extension on a client SKU, but so far I haven't located the files.

Dominant language: PowerShell
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