One of the most frequent asked question on the Exchange forums is to load balance CAS servers. I think the excitements of Exchange being redundant ( DAG) as nature bringing all these good questions and scenarios on the table.
I have learned recently great information in this regard and wanted to pass it on to you guys to clear some of the confusion may exist.
Can TMG/ISA be used to load balance the CAS servers ?
ISA or TMG cannot load balance RPC traffic it can only load balance Internet protocol traffic )-: ( HTTPS,OA)
- It is possible to use WNLB ( windows network load balancing) with HT/CAS server , However there are caveats doing this such as ,
- Scalability more than 8 nodes in WNLB with E2010 CAS is not recommended.
- Network Flooding, WNLB may cause network flooding
- Lack of Service Awareness , the WNLB only is aware of IP is being up/down
So as summary
|WNLB with HT/CAS||Possible but not recommended||Network flooding & lack of service awareness |
|WNLB MBX+CAS||Not Possible!!!||limitation build into Windows (hard-blocked)|
|ISA /TMG||Cannot load balance RPC traffic||Only internet protocol traffic,such as HTTPS,OA|
- RPC Traffic load balance is possible with Hardware load balancer , which obviously will introduce extra $$$$.
As I learn more in this matter I will come back and update this information.
Oz Casey , Dedeal
MCITP (EMA), MCITP (SA)
MCSE 2003, M+, S+, MCDST
Security+, Project +, Server +