Hello, Is there a way of Load balance CAS servers WITHOUT Load Balancer;All I need is failover. Costing considerations.... Best regards KostasKostas Backas-Systemgraph Technologies

You can use the Microsoft NLB; http://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part1.html

You really need a load balancer. Having said that, DNS Round Robin is an option . See: Understanding Load Balancing in Exchange 2010

Hi, You can use the inbuilt feature of windows WNLB that doesn't require any additional costs

If you just want failover you don't need a NLB. If you want fail-over support just use DNS, with CAS Array and OWA\ECP\EAS\EWS records pointing at the primary server. If the primary server fails or needs to be go offline for updates\etc then you just need to update the DNS records to point to the backup server. This will cause ~15 minutes of downtime as clients update their DNS cache. You can use WNLB but I do not recommend it due to many issues my peers (Exchange MVPs, Masters, and consultants) and I have seen. In addition, WNLB is not intelligent, if a server is not responding to request WNLB will continue to send traffic to it. Finally, WNLB and DAG cannot both be setup on the same servers, so to provide HA you need four servers (2 HUB\CAS and 2 MBX). DNS round robin can also be used, but this breaks affinity for many protocols, including RPC Client Access, Outlook Web App, Exchange Web Services, and Exchange Control Panel. Lost of affinity will require clients to re-authentication in most cases. For more info see Understanding Load Balancing in Exchange 2010 as A_D_ pointed out. <If this post helps to resolve your issue, please click the "Propose as Answer" If you find it helpful , mark it as helpful by clicking on "Vote as Helpful" button at the top of this message. By marking a post as Answered, or Helpful you help others find the answer faster>Microsoft Infrastructure Architect, MCSE: M, MCTIP, Microsoft Exchange MVP izzy.org | jasonsherry.org | Twitter: @JasonSherry

You can do couple things without having purchase actual HLB, before I talk about it, I like to mention some of HLB are supper reasonable such as KEMP devices, ( < $2K ) and might worth investing it. Now, as far as your load balancing goes, if you have 2 CAS servers CAS1 and CAS2, assuming you have created CAS ARRAY called Lets say outlook.your company.internal you could create two A record in DNS and point yor CAS ARRAY FQDN to both servers like this CAS ARRAY= outlook.your company.internal DB1= outlook.your company.internal DB2= outlook.your company.internal --------- and so on all DBs are already tagged with CAS ARRAY FQDN --------- RpcClientAccessServer= outlook.your company.internal Now your CAS Server CAS1= 10.10.10.100 CAS2=10.10.10.101 You would have two A records in internal DNS like this.. outlook.your company.internal=10.10.10.100 = CAS1 outlook.your company.internal=10.10.10.101 = CAS2 When you do this since DNS provides round robin DNS query answers back to MAPI ( outlook ) clients if you have 100 MAPI users, 50 connections will go to CAS1 other 50 would go to CAS2 and here is your poor man method of providing Load balancing ( the reason called poor is because there is no application , intelligence in this) Now as mentioned here http://smtp25.blogspot.com/2012/01/exchange-2010-cas-array-simple-dns.html Lower your TTL on these A records to lower the impact. If your CAS1 dies, you still will need to open DNS console and delete the existing A record outlook.your company.internal=10.10.10.100 = CAS1 to point to CAS2 and this means all connections will get picked up by CAS2. If you meant how to do this without having to touch DNS, then you will need to purchase HLB (-: , sorry for keep saying it, but trying to tweak this is Not Supported I wont even mention here some other ways of making this automated but remember as good practice stay away from un-supported scenarios as much as you can Good luck, Ocd Oz Casey, Dedeal MCITP (EMA), MCITP (EA), MCITP (SA) Visit smtp25.blogspot.com Visit Telnet25.wordpress.com This posting is provided AS-IS with no warranties or guarantees and confers no rights.