SIRIS, ALTO, and NAS: 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.

Was this article helpful?

0 out of 5 found this helpful

You must sign in before voting on this article.

Want to talk about it? Have a feature request?

Head on over to our Datto Community Forum or the Datto Community Online.

For more Business Management resources, see the Datto RMM Online Help and the Autotask PSA Online Help .

Still have questions? Get live help.

Datto Homepage