Infrastructure Master & Global Catalog placement

Posted: August 19, 2012 in Active Directory

We might have heard 100 times that we should not keep Infrastructure Master role & Global Catalog in same DC. But most of the admins are not sure about the exact reason behind this. If you know how Infrastructure Master is working, it is really easy to find the logic behind this concept.

Infrastructure Master is used to maintain references to objects in other domain, known as
phantoms. So in a single domain environment it dosent matter where you keep the IM  role. If an object from Domain B is a member of a group in Domain A, infrastructure master in Domain A is responsible for maintaining a reference to this phantom object members. Infrastructure Master used to continually maintain the phantoms whenever the objects they refer are changed or moved in the object domain. It doses this by contacting the Global Catalog (because GC is always up to date and does not have any stale record) and compare the data’s. If Infrastructure Master finds any update info then it updates phantoms and replicates the information to other DC’s.

However if the DC has Im role and you have enabled GC on this DC the the DC has the up to date information Infrastructure Master thinks like there is no changes happened for the phantoms and it will never update any non GC DC’s.


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