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I just finished the 70-294 Kit, and I am left with a huge knownegde gap:

The instructor says that replication taked place 15 seconds after a change is made, and 3 seconds addition for any additional DC.

Likewise, some changes trigger urgent replication between sites (security related).

OK, that makes sence.

Then why, in AD Sites and Services, do the Intersite link objects have an attribute of Replication Schedule? Is there another replication that takes place regardless of changes?

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up vote 4 down vote accepted

There are two different types of replication that take place:

  • Intrasite replication
  • Intersite replication

Intrasite replication is the replication that takes place between DC's in the same site. Intersite replication is the replication that takes place between DC's in different sites (i.e. over WAN links). If you are referring to the "Change Schedule" button under the link objects properties.....

From Microsoft:

Although intrasite replication occurs automatically when an update occurs, replication partners are also contacted once every hour to ensure that changes that might have been missed are replicated.


NTDS Site Settings Properties Sheet - Site Settings Tab

Understanding Sites and Replication

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The 15 second replication occurs for Intrasite replication. Intrasite replication occurs between DCs within the same defined site (same logical subnet) in AD Sites and Services. The replication schedule you are referring to allows you to specify the availability of site link. The site link defines replication between DCs in different sites is called Intersite replication. Additionally there is a site link replication frequency defined in 15 minute increments. So, you could set the Intersite replication to occur every 15 minutes (frequency) all day, everyday. Or, you could say replicate every 30 minutes every Monday thru Friday between 6am and 8pm.

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One thing to add: inter-site replication can also be made to be immediate (which, honestly, should be the default nowadays) by setting the options attribute on the IP site link object to 0x1. – Shane Madden Mar 17 '12 at 19:08
Although, that will only affect password changes, account lockout status (lock and unlock), and changes to the RID master. It's definitely worth enabling, though. – HostBits Mar 17 '12 at 19:25
Those things are always immediately replicated regardless of the options setting. The notify option on the site link replicates all changes immediately between sites on the same 15 second delay. See here, the "Change Notification Between Sites" section. – Shane Madden Mar 17 '12 at 19:38
@ShaneMadden hmm, previous documentation I've seen on change notification specified only those items were affected. I know that password and account locks were immediately replicated, but I've had to enable change notification for account UNlocks. – HostBits Mar 17 '12 at 19:49
And what about the Connection object under Server > NTDS Settings in AD Sites and Services, that refers to the intrasite replication? There is also a schedule there. If I understand that correctly from matrixx333 than besides Change Notification there is an additional replication in case some changes are missed, and the Schedule in the Connection Object represents just that? – Dean Mar 24 '12 at 12:57

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