Exchange 2010 CAS Array advice

I'm doing an Exchange 2010 F5 build between 2 sites, with an internal/external GTM, and internal/external LTM on each site.

 

 

I have one CAS Server per site listening on port 443, and one mail box server per site. Actually, this Exchange 2010 F5 build is for users from another site.

 

 

How should I go about designing this F5 build. Should I split the exchange services between internal and external usage. For instance, outlook, and rpc could be an internal build, on an internal LTM/internal GTM (per-site), whereas OWA, autodiscover are externally accessed, and could be contained on a VIP in an external LTM/external GTM per-site?

 

 

Since, the users will be accessing the Servers from another site, do I need NATTing for the internal VIPs on both LTMs, if I go with the above framework? As per the person who did the installation for Exchange 2010 all Exchange Services both internal/external on the CAS Servers are listening on the same port (port 443)?

 

 

Not sure, if all CAS services should be listening on the same port, but if they are listening on the same port what's the best design option given this scenario. However, if the CAS services are listening on different port numbers, what's the best design option in this scenario to provide for a failover/replicated build on both sites?

 

 

r_dynamo