You are the messaging engineer for your company. Your company has offices in New York, Montreal, and Vancouver.

Your company has an Exchange Server 2007 messaging system. The network consists of a single Active Directory forest. An Active Directory site exists for each office. Each site contains at least one domain controller.

The relevant portion of the network is configured as shown in the following diagram. Also shown in the diagram are the costs for the Active Directory site link.

You notice that all e-mails routed between New York and Vancouver are sent through the WAN link between New York and Vancouver.

You need to design a routing topology to deliver all e-mail messages between New York and Vancouver through the Montreal office. Your solution must maintain the existing Active Directory replication paths.

Which two changes should you recommend? (Each correct answer presents part of the solution. Choose two.)

A.
Configure the Montreal site as a hub site.

B.
Configure the Vancouver site as a hub site.

C.
Configure an Exchange-specific cost of 500 for the link between New York and Vancouver.

D.
Modify the site link cost of the link between New York and Vancouver to 500.

E.
Create three new Active Directory site links. Disable site link bridging on all site links.

F.
Create three new Active Directory site link bridges. Disable site link bridging on all site links.

Explanation:
Choice D eliminated because Your solution must maintain existing AD replication paths.

By default, Exchange 2007 uses AD replication costs assigned to IP site links to compute its routing topology. If the resulting mail flow pattern isnt optimal, use Set-AdSiteLink to assign an Exchange-specific cost to override the AD cost for any IP site link. Message Routing will then consider only this Exchange cost when calculating least cost network paths.

http://technet.microsoft.com/en-us/library/bb232209.aspx