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Application-Aware Processing Tasks Fail in a Kerberos-Only Environment After Upgrading to Veeam Backup & Replication 12

KB ID: 4393
Product: Veeam Backup & Replication | 12
Published: 2023-01-30
Last Modified: 2023-06-01
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Challenge

If you use persistent agents for guest OS processing in a Kerberos-only environment, after upgrading to Veeam Backup & Replication 12, some backup jobs may fail with the error:

Failed to connect to guest agent, failing over to guest agent through VIX
Failed to connect to guest agent though VIX, failing over to guest runtime components

 

This issue may affect the following jobs types:

  • Virtual machine backup jobs
  • Replication jobs
  • Microsoft SQL log backup jobs
  • Oracle archived log backup jobs

Cause

After upgrading to Veeam Backup & Replication 12, the Veeam Backup Server attempts to connect to the Veeam Installer Service and Veeam Guest Helper Service within the Guest OS of the machines using persistent agents and fails. The authentication fails because those services do not have SPNs registered with the Active Directory in the required format.

For Kerberos authentication, each Veeam Backup & Replication services must have two SPNs registered with the Active Directory in the following formats:

  • {ServiceName}/{FQDN}
    Example: VeeamBackupSvc/vbrserver01.tech.local
  • {ServiceName}/{NetBIOSName}
    Example: VeeamBackupSvc/VBRSERVER01

Solution

To resolve the issue, perform the following steps:

  1. Register new SPNs for Veeam Installer Service and Veeam Guest Helper Service and map them to the Active Directory computer objects of backed-up or replicated servers:
    • VeeamDeploySvc/{FQDN}
    • VeeamDeploySvc/{NetBIOSName}
    • VeeamGuestHelperSvc/{FQDN}
    • VeeamGuestHelperSvc/{NetBIOSName}
  2. Wait until the Active Directory replication applies changes.
    You can also force replication if needed.

 

To ensure jobs will process without authentication issues, it is recommended to register SPNs before upgrading to Veeam Backup & Replication 12.

Registering SPNs

Using setspn.exe

You can register SPNs using the setspn.exe utility, for example:

Setspn.exe -S VeeamDeploySvc/server01.domain.local server01
  Checking domain DC=domain,DC=local
  Registering ServicePrincipalNames for CN=server01,OU=Servers,DC=domain,DC=local VeeamDeploySvc/server01.domain.local
  Updated object

 

Using PowerShell

You can also use a PowerShell script to register SPNs for several computer accounts.

The attached archive contains the following files:

  • RegisterVBRGuestAgentComponentsSPNs.ps1 — a script with the PowerShell module
  • Example.ps1 — an example of using the PowerShell module
  • ComputersListExample.txt — an example of the computer account list

You will also need the Active Directory module installed on your machine. For more information, see this Microsoft article.

Purging Negative SPN Cache

After registering new SPNs, you may still get authentication errors for up to 15 minutes because the negative SPN cache on the backup server, guest interaction proxies, and log shipping servers contains old SPNs. You can wait for some time or purge the cache using the following command:

Klist.exe purge -li 0x3e7
Note that the cache will be purged completely, including bad entries.
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