Your network consists of an Active Directory forest that contains one domain. All domain
controllers run.
Windows Server 2008 R2 and are configured as DNS servers. You have an Active Directoryintegrated zone.
You have two Active Directory sites. Each site contains five domain controllers.
You add a new NS record to the zone.
You need to ensure that all domain controllers immediately receive the new NS record.
What should you do?

A.
From the DNS Manager console, reload the zone.

B.
From the DNS Manager console, increase the version number of the SOA record.

C.
From the command prompt, run repadmin /syncall.

D.
From the Services snap-in, restart the DNS Server service.

Explanation:
http://technet.microsoft.com/en-us/library/cc835086%28v=ws.10%29.aspx
Repadmin /syncall Synchronizes a specified domain controller with all of its replication
partners.
http://ivan.dretvic.com/2012/01/how-to-force-replication-of-domain-controllers/
How to force replication of Domain Controllers
From time to time its necessary to kick off AD replication to speed up a task you may be
doing, or just a good too to check the status of replication between DC’s.
Below is a command to replicate from a specified DC to all other DC’s.
Repadmin /syncall DC_name /Aped By running a repadmin /syncall with the /A(ll partitions)
P(ush) e(nterprise, cross sites) d(istinguished names) parameters, you have duplicated
exactly what Replmon used to do in Windows 2003, except that you did it in one step, not
many.And with the benefit of seeing immediate results on how the operations are
proceeding.
If I am running it on the DC itself, I don’t even have to specify the server name.