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Exchange 2010 CAS without load balancer

Posted on 2014-10-24
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Last Modified: 2014-11-29
I have Exchange 2010 SP3 with three servers in two separate sites. We originally designed with two servers and a single mailbox/CAS server in each site and DAG. All active databases are in the same site. To do maintenance or failover everyone would get the new CAS server when their mailbox failed over, and we would often times have to modify DNS for the CAS arrays because older Android clients didn't know how to fail over properly. We have now added a second mailbox server in the main site and I am thinking about how to add the CAS role quickly without requiring a hardware load balancer. My thought is to add the CAS role to the second server, and then just change DNS to point to one server or the other as required for doing maintenance or emergencies. I know that it isn't automated failover, and it isn't load balanced, and I am totally okay with that. I am just looking for a way to be less disruptive when I need to do maintenance on a server. Has anybody tried this, or know of why it would or wouldn't work? Eventually I would like to get Kemp. I know not to do round robin DNS.
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Question by:kevinhsieh
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by:Amit
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You know answers to most of your question. In current environment, changing DNS record seems to be best option. I will say test the concept in test lab and then do it in production.
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by:Gareth Gudger
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Hey Kevin,

If you are looking for a temporary free solution I would look into ARR from Microsoft. It is a free plugin for IIS that allows you to do basic load balancing. You will need a separate box (or VM) to sit in front of Exchange.
http://www.msexchange.org/articles-tutorials/exchange-server-2013/mobility-client-access/iis-application-request-routing-part1.html
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by:kevinhsieh
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@Gareth, I have Exchange 2010 so there is client access using RPC in addition to https.
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by:Gareth Gudger
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Doh! My apologies.
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by:Simon Butler (Sembee)
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DNS entries with short TTL times are the answer here, both internally and externally.
Then you can make the required DNS changes when they are needed, and they will be picked up by the clients quickly.

Hopefully you have an RPC CAS Array for each AD site so clients can be moved around quickly.

Simon.
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We have been able to do a poor person's CAS by configuring two CAS servers, and then changing DNS as needed to point users to one server or the other. Our public DNS service through DNSMadeEasy even handles the public DNS changes for us, which is a major win so that I only need to worry about the internal DNS.
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by:kevinhsieh
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If properly configured CAS servers are in the same site, you can direct clients to one server or the other (or both using round robin DNS) via DNS without the need for a proper load balancer. I load balancer would be better, but DNS makes a nice substitute, especially if the primary issue is for maintenance and not automated high availability.
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