I have been working on Exchange 2010 especially doing a redundant configuration with using the least amount of systems because I am working with a very small environment and I only want good data and access redundancy.
Anyway I found these three articles that really cleared things up:
In these three articles they cover everything you will need to know about load balancing the two servers. It is quite simple actually. Install all roles on both servers. Now you will have to edit the registry to not use a dynamic port for RPC which is used by IMAP and Directory Access:
On the CAS servers, for Mailbox connections, you need to use add a DWORD registry key named “TCP/IP Port” under: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeRpc\ParametersSystem
Figure 8: Adding the required DWORD key on CAS server to configure a static port number
Set the value to the port number to be assigned. In this article we use port 55000, but you are free to choose whatever port you want to use, just remember it should not conflict with other applications using the port. It is recommend you choose a port within the dynamic RPC ranger (1024-65535).
This is from Part 2.
If you set this on both the servers you will need a lot less ports to load balance then before. I am basing this on Kentrox LoadMasters. They are a great product but the only thing they are missing right now is load balancing port ranges. This of course is no big deal after using the registry edit to change it from a dynamic port range to a single static port.
If you have different load balancers you might be able to just load balance the entire servers but it doesn’t matter if you do or not.
Also very good information is in Part 1 about Persistence and in Part 3 about the exact settings of the Kentrox Load Masters.
I also discovered a great website from Microsoft which can help you test outside Exchange connectivity. I know it supports Exchange 2010 but it might work for 2007 as well. Even if the site is made my Microsoft I would for sure not use an account that is actually going to be used with this site. Anyway here is the site and it pretty much tests anything you could.
I hope you have fun,