Exchange 2007 RTM does not support NLB of the Hub Transport rolehttp://technet.microsoft.com/en-us/library/bb510126.aspx however this will most likely change in SP1
How can you NLB the Hub role ?
By default Exchange hub server create 2 recieve connectors– Client (ServerName)– Default (ServerName)

The Default connector is used for all messages that will pass through the hub server. This could [...]