Rescan fails with "Unable to install backup agent: cannot connect to Error: Known agent have the same bios uuid but different connection point ."

KB ID: 4205
Product: Veeam Agent for Microsoft Windows | 2.2 | 3.0.2 | 4.0 | 5.0
Published: 2021-09-10
Last Modified: 2022-08-30
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Scenario Specific Article

This article documents the solution for specific scenarios.

If the scenarios listed in the Cause section do not match your situation, please create a support case.

Challenge

During the rescan of a Protection Group, the following error occurs:
Unable to install backup agent: cannot connect to 192.168.1.55 Error: Known agent SQL-19 have the same bios uuid 59f0f2da-1251-11ec-82a8-0242ac130003 but different connection point 192.168.1.55.

Cause

Scenario 1: Reinstalled OS

The OS was reinstalled on the machine that is displaying this error during rescan.

Scenario 2: Different Machines, Same BIOS UUID

An entirely different machine has been added to the Protection Group. However, those machines have the same BIOS UUID.

The UUID value of a machine can be checked using the following PowerShell cmdlet:

(Get-WmiObject Win32_ComputerSystemProduct).UUID

Scenario 3: Environment with frequent DHCP IP changes

The workstations connect to the network using a VPN solution that assigns a different IP address after each connection, leading to a situation where the cached DNS information stored by the Windows OS of the Veeam Backup & Replication server is out of date.

Solution

Scenario 1: Reinstalled OS

To resolve the conflict, remove the old machine's entry from the Protection Group.

Scenario 2: Different Machines, Same BIOS UUID

Each Veeam Agent computer that consumes a license installed in Veeam Backup & Replication must have a unique BIOS UUID.

If different physical machines have the same BIOS UUIDs, contact the hardware vendor to request assistance in ensuring each machine has a unique BIOS UUID.

 

If Veeam Agent is being used with a VM, please refer to corresponding Hypervisor articles regarding BIOS UUID:

Scenario 3: Environment with frequent DHCP IP changes

OS Level Change

Please be advised that the solution provided for this scenario is shared as a courtesy. Veeam Support strongly suggests you review this change carefully and understand the effects of implementing such change. This change will affect the quantity of DNS requests sent by the Veeam Backup & Replication server.

As this is an OS Level change, Veeam Support is unable to assist with deployment.

In environments where DNS records are updated frequently, it is advisable to consider configuring DNS Aging and Scavenging settings to remove stale records automatically.

By default, Windows OS caches DNS records for one day. The MaxCacheTtl registry value may be adjusted on the Veeam Backup & Replication server in environments with frequent DNS changes to reduce invalid cached information.

The example below demonstrates how to set the DNS Cache TTL to 1 second, essentially disabling all DNS caching.

Key Location: HKLM\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters\
Value Name: MaxCacheTtl 
Value Type: DWORD (32-Bit) Value
Value Data: 1

PowerShell:

New-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters\' -Name MaxCacheTtl -PropertyType DWORD -Value 1

More information

Unsupported Workaround
Unsupported Workaround

This workaround is provided as a courtesy and is not supported by Veeam Technical Support.

Use it at your own risk.

Veeam Technical Support will not assist in the usage or troubleshooting of this workaround.

 

If it is not possible to make the BIOS UUID for a machine uniqe, it is possible to instruct Veeam Agent to use a user specified UUID value from the registry. Use the following PowerShell cmdlets on the machine with the duplicate BIOS UUID.

To enable UUID Failover:

New-ItemProperty -Path 'HKLM:\SOFTWARE\Veeam' -Name EnableSystemUuidFailover -PropertyType DWORD -Value 1
The next command must be modified to place a user-generated UUID where the <UUID> is shown in the command (without carrots).
New-ItemProperty -Path 'HKLM:\SOFTWARE\Veeam' -Name SystemUuid -PropertyType String -Value '<UUID>'
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