server 2025 upgrade cause large files to fail during port forward

Question

server 2025 upgrade cause large files to fail during port forward

Marcel Van Der Merwe 0

when files are port forward after the sever 2025 upgrade they fail

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Erland Sommarskog 133.1K Reputation points MVP Volunteer Moderator

2026-02-18T21:49:17.2333333+00:00

I'm sorry, but your question is anything but clear. First of all what is "server 2025" in this context? I note that a moderator has moved the question to an SQL Server tag, but "server 2025" could also refer to Windows Server 2025.

But apart from that clarification, you also need to explain what you mean with "files are port forward". And what does "fail" mean? Any error message?
Akhil Gajavelly 1,570 Reputation points Microsoft External Staff Moderator

2026-03-06T01:22:15.97+00:00

Hi @Marcel Van Der Merwe ,

As the @Erland Sommarskog mentioned, the question needs a bit more clarification to properly troubleshoot.

In addition to that, since the issue started after the Windows Server 2025 upgrade, please check the following:

Ensure the latest cumulative updates for Windows Server 2025 are installed.

Verify that firewall/NAT or port-forwarding rules were not modified during the upgrade.

Check Event Viewer (System/Application logs) for any network or service errors during the file transfer.

Confirm whether the issue occurs only with large files and if there are any timeout or MTU limitations on the firewall/router.

If possible, please also share the exact error message, file size, and the protocol being used (FTP/SFTP/SMB/etc.), as that will help narrow down the cause.

Thanks,
Akhil
Akhil Gajavelly 1,570 Reputation points Microsoft External Staff Moderator

2026-03-11T05:14:11.52+00:00

Hi @Marcel Van Der Merwe ,

If the issue is still occurring, please share the requested details so the community can assist further. Also, if you were able to resolve the problem, kindly update the thread with the solution as it may help others facing a similar scenario.

Thanks,
Akhil.

1 answer

Your answer

Erland Sommarskog 133.1K Reputation points MVP Volunteer Moderator

2026-02-18T21:49:17.2333333+00:00

I'm sorry, but your question is anything but clear. First of all what is "server 2025" in this context? I note that a moderator has moved the question to an SQL Server tag, but "server 2025" could also refer to Windows Server 2025.

But apart from that clarification, you also need to explain what you mean with "files are port forward". And what does "fail" mean? Any error message?
Akhil Gajavelly 1,570 Reputation points Microsoft External Staff Moderator

2026-03-06T01:22:15.97+00:00

Hi @Marcel Van Der Merwe ,

As the @Erland Sommarskog mentioned, the question needs a bit more clarification to properly troubleshoot.

In addition to that, since the issue started after the Windows Server 2025 upgrade, please check the following:

Ensure the latest cumulative updates for Windows Server 2025 are installed.

Verify that firewall/NAT or port-forwarding rules were not modified during the upgrade.

Check Event Viewer (System/Application logs) for any network or service errors during the file transfer.

Confirm whether the issue occurs only with large files and if there are any timeout or MTU limitations on the firewall/router.

If possible, please also share the exact error message, file size, and the protocol being used (FTP/SFTP/SMB/etc.), as that will help narrow down the cause.

Thanks,
Akhil
Akhil Gajavelly 1,570 Reputation points Microsoft External Staff Moderator

2026-03-11T05:14:11.52+00:00

Hi @Marcel Van Der Merwe ,

If the issue is still occurring, please share the requested details so the community can assist further. Also, if you were able to resolve the problem, kindly update the thread with the solution as it may help others facing a similar scenario.

Thanks,
Akhil.

Answer 1

The context provided does not specifically address issues related to large files failing during port forwarding after the Server 2025 upgrade. However, it does mention that there were issues with domain controllers managing network traffic incorrectly after a restart, which could potentially affect network operations, including file transfers. If you are experiencing problems with file transfers, it may be beneficial to ensure that you have installed the latest updates, as they often contain important improvements and issue resolutions.

For further assistance, consider checking the Microsoft Update Catalog for any relevant updates or patches that may address your specific issue.

References:

Resolved issues in Windows Server 2025

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server 2025 upgrade cause large files to fail during port forward

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