Azure file share regularly disconnects and cannot be reconnected

Question

Azure file share regularly disconnects and cannot be reconnected

CWCPCN 0

Azure file share regularly disconnects and cannot be reconnected for end users

G Sree Vidya 4,250 Reputation points Microsoft External Staff Moderator

2025-08-18T23:45:09.95+00:00
Hi CWCPCN

We understood that you’re having trouble with your Azure file share disconnecting frequently and not being able to reconnect.

Kindly check below details and verify:

1.Azure Files uses SMB over port 445, which is often blocked by ISPs or firewalls.

Use the Test-NetConnection PowerShell cmdlet to check port 445 connectivity.

If blocked, consider:Using Azure File Sync with SMB over QUIC (uses port 443).

Setting up a VPN or ExpressRoute to Azure.

Using Storage Explorer or REST-based tools that work over port 443.

Refer: https://learn.microsoft.com/en-us/troubleshoot/azure/azure-storage/files/connectivity/files-troubleshoot-smb-connectivity?tabs=windows

2.If the client OS doesn’t support SMB encryption and the storage account requires secure transfer, connections may fail.

Use Windows 8 or Server 2012 or later.

Disable “Secure transfer required” on the storage account if encryption isn’t supported.

3.Check the firewall settings on your Azure Storage account. Make sure there are no restrictions preventing access from your clients.

Hope this helps!

Kindly let us know if the above helps or you need further assistance on this issue.
G Sree Vidya 4,250 Reputation points Microsoft External Staff Moderator

2025-08-19T21:57:30.93+00:00

Hi CWCPCN

We haven't heard back from you regarding our last response and wanted to check if you had the opportunity to review our previous post.

Please let us know if you have any questions or concerns. We are happy to assist you.

1 answer

Your answer

G Sree Vidya 4,250 Reputation points Microsoft External Staff Moderator

2025-08-18T23:45:09.95+00:00

Hi CWCPCN

We understood that you’re having trouble with your Azure file share disconnecting frequently and not being able to reconnect.

Kindly check below details and verify:

1.Azure Files uses SMB over port 445, which is often blocked by ISPs or firewalls.

Use the Test-NetConnection PowerShell cmdlet to check port 445 connectivity.

If blocked, consider:Using Azure File Sync with SMB over QUIC (uses port 443).

Setting up a VPN or ExpressRoute to Azure.

Using Storage Explorer or REST-based tools that work over port 443.

Refer: https://learn.microsoft.com/en-us/troubleshoot/azure/azure-storage/files/connectivity/files-troubleshoot-smb-connectivity?tabs=windows

2.If the client OS doesn’t support SMB encryption and the storage account requires secure transfer, connections may fail.

Use Windows 8 or Server 2012 or later.

Disable “Secure transfer required” on the storage account if encryption isn’t supported.

3.Check the firewall settings on your Azure Storage account. Make sure there are no restrictions preventing access from your clients.

Hope this helps!

Kindly let us know if the above helps or you need further assistance on this issue.
G Sree Vidya 4,250 Reputation points Microsoft External Staff Moderator

2025-08-19T21:57:30.93+00:00

Hi CWCPCN

We haven't heard back from you regarding our last response and wanted to check if you had the opportunity to review our previous post.

Please let us know if you have any questions or concerns. We are happy to assist you.

Answer 1

Thanks for posting your question in the Microsoft Q&A forum.

Azure file share disconnections usually happen due to network, authentication, OS compatibility, or policy issues. The most common cause is port 445 being blocked by firewalls, VPNs, or ISPs, which breaks the SMB connection. Other frequent issues include secure transfer/encryption mismatches , firewall or VNET restrictions on the storage account, and credential problems if access keys are not persisted. Disconnections may also occur from idle timeouts, especially on Linux, where keep-alive writes or updated kernel versions help. To troubleshoot, first confirm port 445 is open; if not possible, use Azure File Sync with SMB over QUIC (443) or REST-based tools like Storage Explorer. Also, check storage firewall rules, verify encryption settings, persist credentials, and keep the Azure File Sync agent up-to-date. Reviewing SMB logs and error messages will help pinpoint whether the disconnects are due to network, authentication, or timeout issues

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Azure file share regularly disconnects and cannot be reconnected

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