Network Management

Inaccurate IP results from replicating DHCP servers

This article describes the issue that occurs if you add in 2 DHCP servers where one is a primary and the other is a replica using Windows 2012.

First published date

10/26/2018 5:20 PM

Last published date

5/11/2020 2:57 PM

Overview

This article describes the issue that occurs if you add in 2 DHCP servers where one is a primary and the other is a replica using Windows 2012.

Product section

IP Address Manager

Cause

IPAM does not support the scanning of replicating DHCP servers. It does not recognize that the DHCP servers are linked, nor that the scopes are replicating across - only that the 2nd server is its own entity and the scopes from it are duplicated scopes. Because of this, the DHCP scans do not sync or even run concurrently, leaving the DHCP information on one server can and will have the potential to mismatch the information on the other.

The mismatch of the scans and the scans themselves into non-duplicated subnets can cause issues ranging from SQL deadlocks on updating subnet and IP information as well as DHCP IP conflicts between the results of 1 DHCP server to the other. The former can cause subnet results to not be updated correctly and the latter can cause the IPAM_ConflictData table to grow exceedingly large with false positive information.

The other cause is that DHCP in Windows 2012 has some replicating issues as well as documented here: https://support.microsoft.com/en-us/kb/2751456 (© 2013 Microsoft, available at https://microsoft.com, obtained on November 27, 2018).

Disclaimer: Please note, any content posted herein is provided as a suggestion or recommendation to you for your internal use. This is not part of the SolarWinds software or documentation that you purchased from SolarWinds, and the information set forth herein may come from third parties. Your organization should internally review and assess to what extent, if any, such custom scripts or recommendations will be incorporated into your environment. You elect to use third party content at your own risk, and you will be solely responsible for the incorporation of the same, if any.

Resolution

Remove the replicating DHCP server from IPAM as well as its scopes.
Truncate the IPAM_ConflictData table if it becomes too large.

Disclaimer: Please note, any content posted herein is provided as a suggestion or recommendation to you for your internal use. This is not part of the SolarWinds software or documentation that you purchased from SolarWinds, and the information set forth herein may come from third parties. Your organization should internally review and assess to what extent, if any, such custom scripts or recommendations will be incorporated into your environment. You elect to use third-party content at your own risk, and you will be solely responsible for the incorporation of the same if any.