For most organizations the main benefit of deploying an Exchange Server 2010 Client Access Server array is to minimize downtime.

So when it comes time to update the CAS array members with patches, update rollups or service packs, the update process needs to be managed in a way that prevents all of the CAS array members from being offline at the same time.

Typically this means installing the updates to CAS array members one at a time, allowing each one to complete the update and (if necessary) reboot before updating the next member.

This tutorial demonstrates how to update a Client Access Server array without causing the entire array to go offline at once.  For this tutorial Update Rollup 4 for Exchange Server 2010 RTM is being installed.

Preparing the NLB Cluster for Updates

The first step is to remove the server that is about to be updated from the Network Load Balancing (NLB) cluster.

There are two ways to take a CAS array member our of the NLB cluster:

  • Issue a Stop command to the server
  • Issue a Drainstop command to the server

The difference between the two is that Stop will immediately stop the server regardless of who is currently connected to it, while Drainstop will put the server in a state where it will not accept new connections but will continue serving existing connections until they disconnect.

For urgent updates a Stop command may be necessary, but for planned maintenance a Drainstop has the least potential impact on active client connections to the CAS array.

To issue a Drainstop launch Network Load Balancing Manager, right-click on the desired server, choose Control Host and then Drainstop.

How to Install Updates on Exchange Server 2010 CAS Arrays

When the server has no more active connections it will be in a stopped state.

How to Install Updates on Exchange Server 2010 CAS Arrays

Right click the server and choose Properties.  Set the default state of the server to Stopped.  This will prevent it from automatically starting and accepting client connections after any reboots that the updates require, to allow you time to verify the updates were successful first before rejoining the NLB cluster.

How to Install Updates on Exchange Server 2010 CAS Arrays

Stop Conflicting Services

The Client Access Server role is often installed on the same server as the Hub Transport server role, even when deployed as a CAS array.

Hub Transport servers often run additional applications such as antivirus and anti-spam software that hooks into the Exchange Server services.  These can cause conflicts with Exchange Server updates, for example if a third party application tries to automatically restart a service that it depends on that has been stopped by the update process.

Forefront is one example of this, so for servers running Forefront Protection for Exchange those services can be stopped using FSUtility.

C:\> fsutility /disable

Disabling Monitoring

If the CAS array members are monitored using SCOM or another system this should also be disabled, or placed into maintenance mode before the update is performed.  This prevents unnecessary alarms in the monitoring system due to stopped services or server restarts, and also prevents the monitoring agent from trying to perform any automatic remediation such as restarting services.

Backing Up the Server

Some organizations will require an ad-hoc backup be run of at least one CAS array member before updates are applied.  Others will be happy to rely on the latest scheduled backup instead.  And some will even be satisfied that multiple CAS array members exist and so if a bad update puts one of them out of action there is no outage to end users, and the server can simply be manually reinstalled.

Updating the Server

Install the update following the procedure for that update type.

Update rollups come in the form of a .MSP file (Windows Installer Patch) that is applied to the server.  Simply double-click the file or launch it from a command line window.

Service packs are a complete reissue of the Exchange Server setup files and are installed by running setup in upgrade mode, which can be run in either graphical or command line mode.

C:\> setup /m:upgrade

Both update rollups and service packs can take some time to install, so plan a large window of time for these updates.

How to Install Updates on Exchange Server 2010 CAS Arrays

Verifying the Update

After the update has completed, and if necessary the server rebooted, you should check the server’s health before placing it back into production in the CAS array.

Event Logs – look for error or warning events that have started since the update was applied.

Setup Logs – service packs write a complete setup log file to C:ExchangeSetupLogs

Services – check the Exchange services are running (or at least those that you expect to be running, some such as IMAP and POP will be stopped if you have not explicitly enabled them)

[PS] C:\>get-service *exchange*

Status   Name               DisplayName
------   ----               -----------
Running  MSExchangeAB       Microsoft Exchange Address Book
Running  MSExchangeADTop... Microsoft Exchange Active Directory...
Running  MSExchangeAntis... Microsoft Exchange Anti-spam Update
Running  MSExchangeEdgeSync Microsoft Exchange EdgeSync
Running  MSExchangeFBA      Microsoft Exchange Forms-Based Auth...
Running  MSExchangeFDS      Microsoft Exchange File Distribution
Stopped  MSExchangeImap4    Microsoft Exchange IMAP4
Running  MSExchangeMailb... Microsoft Exchange Mailbox Replication
Stopped  MSExchangeMonit... Microsoft Exchange Monitoring
Stopped  MSExchangePop3     Microsoft Exchange POP3
Running  MSExchangeProte... Microsoft Exchange Protected Servic...
Running  MSExchangeRPC      Microsoft Exchange RPC Client Access
Running  MSExchangeServi... Microsoft Exchange Service Host
Running  MSExchangeTrans... Microsoft Exchange Transport
Running  MSExchangeTrans... Microsoft Exchange Transport Log Se...
Stopped  msftesql-Exchange  Microsoft Search  (Exchange)
Running  vmickvpexchange    Hyper-V Data Exchange Service

Returning the Server to Production

If the update was successful and the server healthy then it can be placed back into production.

Re-enable services such as Forefront Protection for Exchange.

C:\> fsutility /enable

Start the server in the NLB cluster.

How to Install Updates on Exchange Server 2010 CAS ArraysSet the NLB initial host state to Started.

How to Install Updates on Exchange Server 2010 CAS ArraysAnd re-enable monitoring agents and alarms for the server.

After the first CAS array member has been successfully updated you can move on to the next one.

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for


  1. Gold78

    Thanks a ton for your article, excellent information.

  2. Nuwan

    I’m running Exchange Server 2010 SP3 & I have two separate servers one facing internet (CA/HUB) installed & The other ( HUB,CA,Mailbox,) . both version 14.3(buids 123.4)

    I am trying to install Exch 2016 & installation fails it does not recognize first server as service pack installed. it’s end up saying ***All Exchange 2010 servers in the organization must have Exchange 2010 Service Pack 3 or later installed.**

    which both servers I have already updated . appreciates your expert advise on this . thx

  3. andy

    would i need to consider mail queues if patching a HUB/CAS server in an array? or should they just behave?

  4. John_Howard

    I’m running Exchange Server 2010 SP3. How do I move the DAG Witness to another server?

    1. Avatar photo
      Paul Cunningham

      Use the Set-DatabaseAvailabilityGroup cmdlet. Refer to TechNet for the parameters to use when setting the FSW.

  5. LMS

    Hello Paul

    Good article on HUB / CAS update

    We are planning to change the 2 X 1 GB NICs with 10 GB NICs on HUB / CAS servers which are in Windows NLB unicast. We do the changes one server at a time. Here do we need to remove the server from NLB before starting the activity and add it back once we complete the activity or simply change the NIC is enough? The IPs will same

    Thank you

    1. Avatar photo
      Paul Cunningham

      I don’t know. I haven’t touched NLB in a long time and have never had to replace the NIC on an NLB cluster member. Personally I would probably err on the side of caution and remove the member from the NLB cluster, then add it back in after the NIC has been changed. But you should look into it further.

  6. Ben

    What about if you have a multi role CAS/HT and NLB is not used. The load balancers are hardware firewalls, do we need to remove it CAS/HT from NLB, or we can just proceed to update one at a time without removing form LB?

  7. Wes

    Hi Paul,

    Excellent article as usual.

    We are still on Exch 2010 SP1 and are ready to upgrade. Do we need to apply each SP in order ; SP2, then SP3? Or can we install SP3 only (assuming it contains all the updates for SP2)? And would we install the Rollups as well?

    We have 2 edge, 2 cashub using NLB and 2 mbx DAG using windows clustering at one site and then the same at another site. DAGs don’t share across site.

    Thanks for any guidance,

    1. Wes

      Forgot to ask. If we need to install each SP, then do we need to install each on all servers across all sites before moving to the next SP install?

      Thanks again,

    2. Avatar photo
      Paul Cunningham

      Service Packs and Update Rollups are cumulative. You don’t need to install each SP in turn, you can go straight to the latest SP. Similarly with URs, you can go straight to the latest UR for that SP.

      So in your case you would be deploying SP3, followed by UR7.

      You don’t need to upgrade every server in the org with SP3 before rolling out UR7. You could do SP3 + UR7 on each server as part of the same maintenance window.

      Some reading for you:

  8. Harry

    Hi Paul,

    Interesting, I though NLB is no longer working with CAS 2010 anymore. We are running with F5 hardware LB now and constantly have issue with that. Can we use windows NLB (Windows 2008 R2 SP1) with Exchange 2010 SP2 now? Please let me know if there is any issue.

    Thanks as always,

    1. Avatar photo
      Paul Cunningham

      The NLB story for Exchange 2010 hasn’t changed.

      Your F5 appliance is a better solution than NLB. I suggest fixing your F5 config or contacting F5 support to help you out with it.

    2. Server System Engineer

      What sort of problem that you have with F5 ? Please share it here.

      My 2x HT/CAS Exchange Server 2007 SP3 still having a problem with F5 hardware load balancer.

      The problem is that it cannot send email with more than 100 recipients, so bulk email sending is still the problem here. no solution so far apart from sending the email in multiple times in a chunk of 99 recipients.

  9. Yous

    After Drain stop and stopping the server in Cluster, when i updated the server, and attempted to start host in NLB, and cause to automatically stop another host in the cluster


  10. Rahmat

    thank you for your nice post

  11. Zac Hooper

    Hi Paul

    Nice consie doc for exchnage rollups, any guidance/process on Windows, IIS and Exchange patches together and how the affect one another(Excluding the lengthy KB articles).

  12. Hein

    Sorry for spamming but how long would it take for the NLB to activate the cas server again? It is now converging with status pending.. and it feels like it is either taking its time or quite its job and when awol.

  13. Hein

    I read the fsutility /disable step but unless my eyes are decieving me there is no /enable step mentioned?

    Other then that it is a excellent how-to. Kudo’s, +1, like and what else the kids nowadays hand out to say thanks 🙂

    1. Hein

      Okay i admit.. too late too little sleep + lack of coffee.. i read the fsutility /enable now *sheepish grin*

  14. Vino


    I am planning to upgrade exchange server( 2 MB, 2 Hub/Cas) from sp1 to sp2 , rollup 4. Is there any important things to be considered before upgrading.. Why iam asking this now my exchange working fine without no issues but for safety purposes to match the latest patch iam planning to upgrade…

    Please give me your suggestion…

    Thanks in advance…..

    1. Avatar photo
      Paul Cunningham

      Yes, every Service Pack and Update Rollup contains some “gotchas”.

      I’d recommend reading the release notes that Microsoft publishes with each one, reviewing the fixes that are included and the new features that are added.

  15. Carol Ostos

    Help!! I just noticed my CAS/HUB servers are running SP1 Rollup 2 but I must have forgot to apply RU 2 to my MBX servers, I can just do passive node first, failover, then active node? I know there is a particular order when it comes to updating Exchange so I just wanted to confirm, should be CAS, then HUB and finally MBX right? Thanks!!!!

  16. Vigneswaran Chandramohan

    Hi Paul,

    After givng “drainstop” command, how much time do we need to wait? In my case NLB is saying “stopping” but it is not going to “stopped”.


    1. Avatar photo
      Paul Cunningham

      Drainstop will wait until any active client connections have closed. So if you’ve still got clients connected it won’t finish stopping that server.

  17. Yves

    Great article,

    I only think you made a little typo error.
    It should be fscutility /disable (instead of fsutility).


  18. Brenda


    I’m having a big issue here and I’m pretty much out of MS support hours – I created a DAG on my mailbox server Friday night, everything worked fine, sat at 9:54 at my BB goes down and I’m basically being told by BB support that its a MS issue. My BES, is resolving the CAS/ names and IP address but it resolves it to the CASE ARRAY name correct, well I tried adding a host file on my BES and none of this worked, my outlook suddenly started doing te same thing on Sat, where it is resolving to the CAS ARRAY name – can you shed some light on this for me please

    1. Avatar photo
      Paul Cunningham

      Brenda, I don’t really understand your question the way it has been written. But it seems like it doesn’t relate to the article above, so I would suggest that you start a thread in the forums instead.

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