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Configuring Exchange Server Roles

Tacobell2000 used Ask the Experts™

I need clarification please on the Exchange setup I’ve inherited. The setup is:

•      1 AD Domain
o      4 AD sites (Each Site Contains an Exchange Server)
o      All Mail comes in to a hub site and it gets distributed to all other sites
¿      The Hub site has 2 Hub transport server roles installed
•      One is hardware and also has the CAS Server role
•      The second is a VMWARE and it is running the Hub Transport Server role.
o      Both Hub Transport servers are not Load Balanced

Message tracking is showing me that both hub transports are sending and receiving messages.
There was 158 messages in queue on 1 of the transport servers and rebooting the server cleared the queue. (I did not do this)

My questions are:
Would it not be better to uninstall the HUB transport role on 1 of the Servers? Install the Hub Transport Role on a VMWARE and have both these server on an NLB Cluster? Or perhaps just install the CAS server role on top of the Hub Transport role and have both these servers NLB Clustered? Can this be accomplished on hardware and VMware ?
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You do not need to NLB the Hub transport servers and there should be no issue with using a combination of VMWare and physical hardware.  I am wondering if the messages are stuck due to a large message or a corrupt message.  The dual hub transports provide the redundancy for routing messages.  Are you going through an SMTP gateway and that is routing to the Hub Transports or do you have dual MX records for the hub transports?


Actually, there is an smtp server running IIS 6.0 on a W2K3 server between the Hub Transport and EHS (Forefront online services). this server is sending all outbound messages to EHS. That server had to be rebooted.

So it was the outgoing message queue to the gateway SMTP server that was stuck?  I am thinking the issue was simply the W2k3 server SMTP service just stopped responding.  

But to get back to your original question, the way you have the hub transport service configured in your organziation is sound and I would not recommend any changes at this time.  

Per the article below - NLB is recommended/support only in the following scenerios:


Exchange 2007 Service Pack 1 (SP1) supports the use of Network Load Balancing (NLB) to achieve high availability for specific types of connections to the Hub Transport server role. NLB can be used to provide high availability in the following scenarios:

Load balancing of inbound SMTP connections for POP and IMAP client connections to the default Receive connector named "Client <Server Name>" that is created only on Hub Transport servers.

Load balancing of inbound SMTP connections for applications that submit e-mail to the Exchange organization."


Thank you sir!