You are the messaging engineer for your company. The company has a main office and four branch offices. You are currently running Exchange Server 2007. Each office contains two clustered Mailbox servers, one Hub Transport server and one Client Access server. You need to recommend a solution for e-mail delivery redundancy on your network in case a Hub Transport server fails. Which solution should you recommend?
A.
In each office, install the Client Access server role on a new server.
B.
In each office, install the Hub Transport server role on a new server.
C.
Run the Setup.exe /roles:HT command on each active clustered Mailbox server.
D.
Run the Setup.exe /roles:HT command on each passive clustered Mailbox server.
Explanation:
Install multiple Hub servers in the same AD site to provide fault tolerance and load balancing. By default, connections are automatically load balanced across all Hub servers in any site. If one goes down, the remaining servers take up the slack. Should all Hub servers go down, messages are queued until either one of the Hub servers re-activates or the mail expires.Achieve load balancing for outbound connections to remote domains by selecting more than one Hub machine in any site as source servers for the Send connector. Load balancing doesnt occur when these source servers are located in different AD sites.
http://technet.microsoft.com/en-us/library/bb124398.aspx
Deploy multiple Hub servers for high availability of internal transport. Resiliency has been designed into the Hub role in the following ways:
1. Hub server to server communication inside an organization automatically load balances between all available servers in the target AD site.
2. Mailbox server Mail Submission service automatically load balances between available Hub servers in the same site.
3. The UM server automatically load balances connections between available Hub servers in the same site.
3. The Edge server automatically load balances inbound SMTP traffic across all Hub servers in the site to which its subscribed.
For additional redundancy (for example, apps needing an SMTP relay), create a new DNS record, assign an IP address, and use a hardware load balancer to redirect that IP address across multiple Hub servers. In Exchange 2007 SP1, Hub server client connectors likewise support NLB.
http://technet.microsoft.com/en-us/library/bb124721.aspx