Windows 2008 R2 Forest

Just wondering what the best practice is here.  I have two sites, one is in Dublin and the second is in London.  Dublin has an IP range of and London is  I have a forest/Child setup e.g. Forest is and then the children are and  I wanted to have a DC for the domain in each site (for DR purposes) but I'm not sure how that will work in Sites/Services having two DCs for the same domain being associated with a different subnet.  Plus I will be installing Exchange 2010 in both Dublin and London.

Any ideas?
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minniejpAuthor Commented:
Any thoughts?
Steven WellsSystems AdministratorCommented:
you can have two DC's for the same domain in different subnets as long as you configure the sites and services correctly association the site wiht the subnet.

Ie, create a site in AD sites and services called Dublin and associate with that site and do same for London.
then move your DC's in to those sites if needed
exchange will work fine as long as you have above setup.
minniejpAuthor Commented:
Thanks for your reply.  So to confirm

I will create a site called Dublin and associate the site with  I will then add the domain controller for the Dublin domain to the Dublin site and also one of the domain controllers from (the one who has the IP  I will then create a site for London and associate to it and add the cd for London and the other dc for to it?

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Steven WellsSystems AdministratorCommented:
Yes.  That will work.  That is how active directory works.

Have a read up about forest sites and services in the above link.
Steven WellsSystems AdministratorCommented:
minniejpAuthor Commented:
Hi Steven,

I did as you suggested but now on the London DC I am getting this error:

Starting test: Knows of Role Holders
Server(which is the schema master and resides on the Dublin subnet) failed with error 1722,
The RPC Server is unavailable....
Warning: Server is the schema owner, but is not responding to DS RPC bind.
LDAP search capability attribute search failed on server return value = 81
Warning: server is the schema owner, but is not responding to LDAP bind
Warning: Server is the domain owner, but is not responding to DS RPC Bind
Warning: Server is the domain owner, but is not responding to LDAP bind

Replication to the other London DC isn't working to the schema master in Dublin, The replication generated an error 1256

Any ideas?
Steven WellsSystems AdministratorCommented:
Sounds like you have DNS issue.
Steven WellsSystems AdministratorCommented:
I would check your servers have updated their DNS entries correctly.  Especially in the name servers tab.  Ensure the DNS settings in the TCP/IP confit are correct and reboot server.

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Guy LidbetterCommented:
hi minnieJp,

This sounds like it may be a networking issue... are teh two sites linked and are there firewalls between them?

Check connectivity for the below Ports which need to be opened for Active directory to function properly
UDP Port 88 for Kerberos authentication
UDP and TCP Port 135 for domain controllers-to-domain controller and client to domain controller operations.
TCP Port 139 and UDP 138 for File Replication Service between domain controllers.
UDP Port 389 for LDAP to handle normal queries from client computers to the domain controllers.
TCP and UDP Port 445 for File Replication Service
TCP and UDP Port 464 for Kerberos Password Change
TCP Port 3268 and 3269 for Global Catalog from client to domain controller.
TCP and UDP Port 53 for DNS from client to domain controller and domain controller to domain controller.
Also refer to the below links which will explain this in more detail.
Port used in Active directory Replication.
Active directroy and Firewall ports,
Active Directory Replication over Firewall


minniejpAuthor Commented:
Thanks for all the replies, Steve, I added a DNS Zone and all the errors have now disappeared.

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Windows Server 2008

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