Veeam Backup & Replication | 9.5 | 10 | 11 | 12
Veeam Backup for Microsoft Office 365 | 2.0 | 3.0 | 4.0 | 5.0
Veeam Backup for Microsoft 365 | 6.0 | 7.0
Veeam Agent for Microsoft Windows | 2.1 | 2.2 | 3.0.2 | 4.0 | 5.0 | 6.0
Veeam Cloud Connect | 9.5 | 10 | 11
Data transfer is failing across a connection that is protected by an advanced firewall. The firewall uses signature-based detection. Relevant features may have names like antivirus, anti-spyware, intrusion prevention, or application control.
This may affect any make or model of firewall with similar features, but support cases have been opened for:
Any type of data transfer may be affected. This problem may manifest in a wide variety of error messages and failure patterns. It may appear random, or consistently.
For the Veeam Backup & Replication product, this can affect Backup, Backup Copy, and Replication jobs. One common failure pattern is for the transfer of specific VM disks to consistently fail at or around the same percentage of completion.
Common error messages include:
An existing connection was forcibly closed by the remote host.
Unstable connection: unable to transmit data.
Depending on the job type and the version of Veeam Backup & Replication, connection failures may cause the job to fail immediately, or the connection may retry several times. While the connection is retried, the job may appear to be frozen because it is unable to transmit data. For more information, see:
Resume on Disconnect
Backup Copy: Automatic Job Retries
WAN Acceleration: Data Transport on WAN Disconnect
With Veeam Backup for Microsoft 365 this issue may appear with an error message:
A blocking operation was interrupted by a call to WSACancelBlockingCall
It is advisable to begin by reviewing any logging available from the firewall to identify interactions and false detections that interfere with Veeam software data transmissions. Then, create exclusions for Veeam data traffic.
In most cases for Veeam Backup & Replication, Veeam Agent for Microsoft Windows, and Veeam Agent for Linux, the relevant traffic will be between servers when data is transferred over the transport ports of 2500-3300. This range can be configured for each managed server in the backup infrastructure settings.
Cloud Connect Service Providers should create exclusions for data traffic sent to Cloud Gateways on port 6180 (TCP and UDP).
For Veeam Backup for Microsoft 365, this can be affected by data be transferred over port 443.
For more information on port ranges, find the relevant product or component user guide in the Help Center and consult the Used Ports page.
For information on how to configure exclusions on a specific firewall appliance, please contact the firewall vendor.
This form is only for KB Feedback/Suggestions, if you need help with the software open a support case