Server 2016 - DHCP Event ID 20291 (Reject Reason Unknown) + DHCP Event ID 20292 (Outdated Binding Information)

2019-11-18

Question

_{Monday, November 18, 2019 1:39 PM}

Good day

I have had a lot of 20291 and 20292 errors crop up on DCs (DC2 - mainly 20291) which is also the PDC. It is in a load balancing state with DC1 (most errors of 20292) - (both DC's on-prem).

A lot of sources say to deconfigure then reconfigure the failover relationship for each scope. I'm nervous as running through the options, it says it will delete the scopes from the partnered machine. There are DHCP backups but still, these are all live in production.

I've tried the powershell script Invoke-DhcpServerv4FailoverReplication - no change. Refreshed, reconciled and verified entries, no change. Manually deleted bad addresses where found in all scopes on both DC's, no change. Set the options to check for conflicts. No change.

What can I do further to resolve these errors that are clogging up my event logs?

Kindest regards

Darren

All replies (3)

_{Tuesday, November 19, 2019 9:58 AM ✅Answered}

Hi,

The following situations may occur the Event 20291:

You configure the servers as a failover cluster.
You set up multiple DHCP scopes and multiple IP networks.
You put a client computer on one of the IP networks and confirm that it receives an IP address from one of the scopes.
You move the client computer to a different IP network.

To solve the error, you can do the following steps to have a test:

The DHCP failover need a Time Synchronization between servers, you could check the time on the 2 server.

And you can try to delete a scope on one server, then replicate failover scope, are they worked appropriately or not.

Also please install the lasted KB patches to check if the problem is solved.

Hope this can help you, if you have anything unclear, please let me know.

Have a nice day!

Ellen

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_{Wednesday, November 20, 2019 7:15 AM}

Good morning Ellen

Thank you for the feedback.

Checking my event viewer, the 20291 errors have cleared up. What I did was only delete one super scope and sub-scopes in it, then from the partner DC, configure failover from that side. No other scopes were deconfigured and reconfigured for failover. I also ran reconcile of the dhcp database.

Other than that, no other changes were effected.

I am unsure as to why it has cleared up, or why there were reject reason unknown errors in the first place.

* I am unsure as to the clusters setup and do not know how to check that.

* There are multiple DHCP scopes and superscopes.

* I am unsure as to what you mean for multiple networks? Are you referring to multiple WiFi networks and the LAN?

* I confirmed that addresses are being handed out between DC1 and DC2 (load balanced). One IP address that was rejected for reason unknown on DC2 was passed to DC1, which assigned it an address.

* I am unsure what you mean about moving a client computer to a different network. Do you mean if they switch between various WiFi networks or connect to the LAN?

* The PDC (DC2) is configured as the primary time controller (it points outwards to a time server), and all DC's are regulated by policy to look at the PDC for time (confirmed that sync works on all DC's - basic domain hierarchy setup).

* All machines are fully patched and up to date, all are on the server 2016 platform.

Thank you very much for your help and assistance.

Kindest regards

Darren

_{Wednesday, November 20, 2019 9:27 AM}

Hi,

*>>Checking my event viewer, the 20291 errors have cleared up. *

Do you mean that the error are fixed up?

If yes, we advise you to continue observer the DHCP failover.

If there is still error, please feel free to contact us.

As a support engineer, I will try my best to assist you.