I have a 2010 Exchange server on a 2008 R2 domain controller (DBXDC02.dbx.local). I have recently introduced a 2012 domain controller (DBXDC03.dbx.local) with the intension of migrating the exchange from 2010 to 2013 on the new DC. The prerequisites before migrating is to have exchange 2010 at SP3 level. As mine is not, I have tried to upgrade but come across the following error when running the installer:
Setup encountered a problem while validating the state of Active Directory: An active Directory error 0x51 occurred when trying to check the suitability of server 'DBXDC03.dbx.local.' Error: 'Active directory response: The LDAP server is unavailable.'
This error appears when checking the prerequisites and the error is seen under the "Organization Prerequisites", the "Hub Transport Role Prerequisites", Client Access Role Prerequisites" and the "Mailbox Role Prerequisites".