Exchange 2007 SP3 - CAS Server

We are using NLB, and the VIP is say:  webmail.abc.com = 172.12.10.60

CAS01 = 172.12.10.56
CAS02 = 172.12.10.57

All the above is in DNS with MX records

My concern is when we reboot CAS02,     OWA goes down, isn't NLB supposed to be if CAS02 goes down CAS01 takes over or if CAS01 does down CAS02 takes over.

That is not the case for us, can anyone give me a suggestion on what I have to check to see if everything is configured correctly.

Server 2008 R2 - Exchange 2007 SP3

thanks
techgeniousAsked:
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Delphineous SilverwingGood Ol' GeekCommented:
This occurs because of the Broadcast method being used on the NLB.  You are likely setup for Unicast, which may have this impact in some environments.  Try using IGMP multicast - Cluster Properties > Cluster Parameters.
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techgeniousAuthor Commented:
We are using Multicast,  your suggestions is IGMP multicast?
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Delphineous SilverwingGood Ol' GeekCommented:
Be warned that some switches do not like it and will treat it as a broadcast storm.  Give it a shot off-hours to ensure it doesn't impact your environment.

Otherwise, your switch may need some configuring to help it understand which ports are for multicast traffic.

In case you haven't seen it - This TechNet article is a good read for understanding NLB multicasting.  http://technet.microsoft.com/en-us/library/ff849728.aspx#ClusterMode
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techgeniousAuthor Commented:
Now will this solve our issue when CAS02, goes down, OWA will be available, because right now when CAS02 goes down,  no one can access OWA
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Delphineous SilverwingGood Ol' GeekCommented:
The issue is primarily caused by the network hardware not handling the NLB traffic across nodes correctly.  Resolution may be changing the communication method of the cluster or it may be a configuration change on the network switch.

How old is the network switch?  If you are using Cisco FEX technology, hanging the cluster mode will not make a difference if the firmware is not current.
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techgeniousAuthor Commented:
thanks I would have to check with the Cisco engineers and see what we have.
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techgeniousAuthor Commented:
Thanks for the answer, my other question is if our network device does not support NLB, and say CAS02 goes down is there anyway for our clients to access OWA, do we have to manually do something?

thanks
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Delphineous SilverwingGood Ol' GeekCommented:
I cannot say for certain.  It depends on the capabilities of your network hardware - Unicast could work for you for that matter.

Here's another technet article to shed some additional light on Unicast versus Multicast.
http://technet.microsoft.com/en-us/library/cc782694%28v=ws.10%29.aspx
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