Infrastructure Master question (FSMO / 70-640)

EasyMac308

Hi folks,

I'm just wondering if someone can shed some light on this for me. I'm studying for 70-640 and the material says that the Infrastructure Master Role must be placed on a DC that's not a GC server unless they're *ALL* GC servers. Why is that? The material doesn't say. Thanks!

Psoasman

If I remember right, the infrastructure master's job is to compare the objects in its domain with objects from other domains in the forest. It compares the objects against the global catalog. When an object is changed, the global catalog is updated with that change. If your IM finds that an object is out of date, it will ask the global catalog for the updated info. The IM takes that updated info and replicates it to the other DCs in the domain.

Microsoft says that if the IM and GC are on the same server, the IM won't find objects out of date, so any changes won't be replicated to the other DCs in the domain.

The exception would be if you only had 1 DC in the domain, or if all of your DCs are global catalog servers.

btw: nice to see another person from WA state.

EasyMac308

Hmmm.... OK, thanks for the clarification. (And the welcome).

Claymoore

In a single forest / single domain deployment - the majority of AD deployments - there is nothing for the Infrastructure Master to do so it can be on a GC. If all of the DCs are GCs, even in a multi domain deployment, if all DCs are GCs there is no worry about stale cross-domain references so the Infrastructure Master can be on a GC. I can't think of a good reason why a DC should not also be a GC, in fact I have only seen problems arise when admins decide not to make every DC a GC. It's easiest to make every DC and GC and not worry about who holds the Infrastructure master role until it is time to upgrade the schema.

Because a global catalog maintains a partial copy of every object from every domain in the forest, the requirement to maintain any cross-domain references is eliminated. Therefore, if the infrastructure master is running on a global catalog server, it never finds any cross-domain references in its local database. Consequently, the infrastructure master is not able to determine which cross-domain references are stale, and it will not provide updates to any other domain controllers in its domain. For this reason, the infrastructure master should not run on a global catalog server in a forest that contains multiple domains. The following exceptions apply:

• If every domain controller in a domain is a global catalog server, no cross-domain references exist, and the problem in the impact statement will not appear.
• If a given domain in a multidomain forest contains only one domain controller, the domain controller is the infrastructure master itself, or a global catalog. Therefore, the issue is not relevant.

AD DS: The infrastructure master for this domain should be held by a domain controller that is not a global catalog server
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