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Agentless Backups: Critical Backup Failure: HTTP: Could Not Connect to Host



Backup attempts of a virtual machine through the agentless backup feature fail with, "Critical backup failure: HTTP: Could not connect to host," or "Cannot connect to the host \- aborting backup."


  • Datto SIRIS
  • Agentless Backups


  • The Datto appliance cannot reach the host hypervisor.


  1. Verify connectivity between the Datto appliance and the hypervisor, and that networking requirements are satisfied as defined in the SIRIS, ALTO and DNAS Networking & Bandwidth Requirements article.
  2. Restart the vCenter service using the vSphere console.

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