Hi Team,

I would like to clarify on Extending Schema from different AD site.

Question 1 : Can we extend the Schema from a member server from different AD site by using the Domain Controller Parameter? 

Setup /PS /IAcceptExchageServerLicenseTerms /Domaincontroller:Server1.XYZ.local

Note: Server1.XYZ.local has Schema Master role in different AD site.

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Before you extend your schema, there are a few things to keep in mind:

• The account you're logged in as needs to be a member of the Schema Admins and Enterprise Admins security groups.

• The computer where you'll run the command to extend the schema needs to be in the same Active Directory domain and site as the schema master.

• If you use the DomainController parameter, make sure to use the name of the domain controller that's the schema master.

• The only way to extend the schema for Exchange is to use the steps in this topic or use Exchange 2013 Setup. Other ways of extending the schema aren't supported.

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https://technet.microsoft.com/en-us/library/bb125224(v=exchg.150

The article you quote seems to say you cannot extend the AD schema for Exchange 2013 from any site except the one with the Schema Master. At one point the statement is a recommendation, then later a must.

This must be specific to Exchange. I have never seen this recommendation elsewhere. Of course, all schema updates are done on the one forest wide Schema Master (the DC with the Schema Master FSMO role). I guess you should have good connectivity with this DC for the large number of updates required for Exchange. Still, I suspect it is a recommendation.

Edit: I should add that any Schema update is a one time operation that cannot be undone. I suppose if there is a risk, no matter how small, of an interruption that would leave the schema update incomplete, that would be very difficult to recover from. If at all possible, I would follow the recommend

You can extend the schema from anywhere. It is recommended to do it on the schema master (which you should), but not a requirement.

If the schema master falls down during an update, it will continue the extension after it comes back.

Back out plan: forest recovery.

Mike