DHCP Failover max Relationship Issue Error 20128

Question

I have tried to configure more than 25 Scopes from several DHCP-Servers to connect to a single HotStandby-DHCP Server.
The next added Scope gave me this: Error 20128

Add-DhcpServerv4Failover : Fehler beim Erstellen der Failoverbeziehung "server1 bla" auf dem Server "xxxxx1".  
In B:\Scripts\Tools\DHCP\Migrate-DHCP-Failover.ps1:48 Zeichen:1  
+ Add-DhcpServerv4Failover -ComputerName $Source  -PartnerServer $Desti ...  
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
    + CategoryInfo          : Grenzwertüberschreitung: (xxxxx2:root/Microsoft/...erverv4Failover) [Add-DhcpServerv4Failover], CimException  
    + FullyQualifiedErrorId : DHCP 20128,Add-DhcpServerv4Failover  

There is a limit built in DHCP-Failover, but no explanation can be found via Google.
Is there a Reference available about this topic more than simple API Error Codes ?
(https://learn.microsoft.com/en-us/previous-versions/windows/desktop/dhcp/dhcp-server-management-api-error-codes)

My goal is to provide a HotStandby-Backup for >200 Scopes, this is not limited by WMI-Connections afaik...

Answer 1

We found the the reason for the error:

It was a wrong usage of the command "Add-DhcpServerv4Failover", this is meant to connect a whole server, not a single scope. But it allows you to do many connections to the same server, that is maybe a design flaw. It can spoil all of your 31 available connections on single scopes on the same server....

In fact, you can connect 31 DHCP Servers to your partner DHCP by using the command "Add-DhcpServerv4Failover".
And..You can add >200 Scopes per Server as you tested with "Add-DhcpServerv4FailoverScope" referring to the same name.

This command is initializing the Failover-Connection with 2 Scopes for example:

Add-DhcpServerv4Failover -ComputerName "server1" -Name "Server1-Failover" -PartnerServer "centralDHCP" `
-ScopeId 10.10.10.0,10.20.20.0

additional scopes from the same server must be added by this command under the same Name:

Add-DhcpServerv4FailoverScope -ComputerName "server1" -Name "Server1-Failover"-ScopeId 10.10.11.0,10.20.21.0

...The next Server gets a new connection name as communication channel "Server2-Failover".

Thank you Jiang for your efforts, i recommend using powershell doing such jobs...

Answer 2

Hi,
I have tried to add 201 scopes in my lab, and it appears there is no limit amounts of scope built in DHCP-failover relationship with my TWO DHCP servers. I am wondering how many DHCP servers you are goanna use to add scopes to a single Hot Standby-DHCP Server?

Best Regards,
Mulder Zhang

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