Introduce another CAS/HT server on the cas array on NLB

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I have a single server CAS array (CAS/HT) on NLB, i'm planning to introduce another server for the casarray (again CAS/HT). I wouldn't want any client requests for both the cas/ht server until i configure the server properly. How do i avoid client request for my cas/ht until i fully configure it???



That would be completely handled by your NLB Solution. Many solutions provide ways to drain stop or deactivate specific members.

To be honest however, until you add the box to the NLB it will never get a request, meaning you can safely add it to your CASArray and it will simply site there. The CASArray cmdlet itself does nothing to " activate" the NLB to start recieving requests.


From your question I assume that you already have a CAS array with a single server and you want to add another node to the array .

so to stop all client access on your server Stop the Microsoft Exchange Active Directory Topology Service from the services console, consequently This will stop all exchange services till you finish the CAS Array configuration. Once finished start this service again.

Mohamed Dawy

MCP, MCSE 2000 , MCSA 2000 ,MCSA 2003 , MCITP , MCTS , MCT

Scott Feltmann

Like Justin Said,

If the New server isn't part of the NLB configuration it will not get a request.

I believe where a lot of confusion is occurring is that when an Administrator uses the command “Get-ClientAccessArray” they end up seeing something like this:

Name Site Fqdn Members
——– —— ——- ————–
Casarray Sitename {CAS1, CAS2, CAS3}

Really, the Members are NOT actually members of the CASArray but rather the Client Access Servers that happen to be in the Active Directory Site where the CASArray is configured. The NLB configuration is what really controls the membership of a CASArray! So, again, to remove a Client Access Server from a CASArray you simply remove it from the NLB configuration!

I have a few articles on CASArrays if you like to read:

SF - MCITP:EMA 2007 and 2010, MCTS: Exchange 2010, Exchange 2007, MOSS 2007, OCS 2007 --


Scott, justin,
Thanks for the reply. i wonder, when i install anohter cas which is not yet part of NLB, the SCP would still recognize the new server as cas as it has registered in the SCP. !!

I wonder what should be the internalnlbbypassurl - should be? does it really matters?



You are correct: the SCP will still be there for autodiscover. However, remember the final CAS selected as an endpoint is actually set by your mailbox database (remember setting up the association when you setup the first CAS Array). So even if a client connects temporarily via an auto-discover SCP call it will basically go: connect to CAS--> find mailbox on store --> store points to closest CAS (aka cas array address that you set) --> client conencts to CAS Array name (which points and NLB VIP).

The only real risk you run is if your SCP record doesn't match the certificate assigned to the CAS. In other words the SCP is still pointing at Server1.domain.local and you replace the certificate on the CAS with one that does not contain that name. During that period, you risk an SSL popup error if a outlook client happens to be running an autodiscover query at that moment.

You can fix that by updating the SCP URL via powershell at the same moment you assign the new certificate.


Thanks Justin
i wonder what should be the internalnlbbypassurl. In one of the article at; it says, if the cas are behind NLB, it should be untouched. i wonder is it ok?


Brian Day MCITP

InternalNLBBypass should always be the FQDN of the CAS server.

The SCP is only used by clients for the Autodiscover process. Ironically only the oldest SCP record returned to Outlook is used (they're sorted by age and it starts at the oldest one). Your oldest CAS server's SCP record will always be the one being hit unless that CAS server is down at the time the client tries to contacts it. You can avoid your oldest CAS server from taking all of the AutoD load in large environments by using a load balanced name for the AutodiscoverServiceInternalUri value. This also makes sure if CAS server is down you don't have to wait for AutoD to timeout before it uses the nest CAS server, which would introduce a delay for the user.

This is assuming we're not dealing with multiple AD sites with Exchange servers and users in different AD sites. What SCP records are used is a little different in that situation.

Microsoft Premier Field Engineer, Exchange
MCSA 2000/2003, CCNA
MCITP: Enterprise Messaging Administrator 2010
Former Microsoft MVP, Exchange Server
My posts are provided "AS IS" with no guarantees, no warranties, and they confer no rights.
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