E2K10 SP2 RU3 cross site failover - Is DNS record update requirement? or recommendation?

Posted on 2013-11-22
Medium Priority
Last Modified: 2016-10-25
My 4 node DAG spread across two AD sites.
2 in Primary and other 2 in Secondary site.
We also have 2 CAS in Primary and other 2 in Secondary (Netscaler VIP in each site with different DNS name).

This blog says DNS IP change from Primary CAS to Secondary is "recommended" or "guide line". Not definitely a "requirement" if I've read correctly. It's reasonable because Primary CAS is totally down, no one can tell Outlook the new CAS name in Secondary site.


"changing the primary datacenter's DNS records to point to the IP addresses in the secondary datacenter, that is still our recommendation"

However this blog guy succeeded to perform the event WITHOUT changing DNS record.


It seems Outlook retrieves the new CAS name from AD without relying on primary CAS name.

I'd like to understand :
- It looks DNS change is not "requirement". Why MS guy still keep this procedure as "recommendation"?
- What happen if we don't follow MS guidance?
- What is the technical query processes that Outlook to get CAS name. Where's the attribute that Outlook determine the new CAS name in new site?

Cross site failover is an event in very extreme situation and we most probably can't expect DNS team guy to be available timely. It's much better if we can just rely on AD replication.
Not sure why the guidance keep this process manual.

Question by:kimakabane
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 2
LVL 63

Accepted Solution

Simon Butler (Sembee) earned 750 total points
ID: 39668775
All the designs and procedures I have written have involved updating the DNS record.
I wouldn't depend on Autodiscover picking up the change.

I do this for speed - if I have done cross site it is quickest to update the DNS entry (which will have the lowest TTL time).

The client will find the new server from the information within the domain related to the CAS Array. Remember the CAS Array is two parts - the DNS entry and the configuration in Exchange (new-clientaccessarray). CAS Arrays are also AD site specific. Therefore if you change the database activation value, then the clients should find the new CAS Array for that site.

I will admit it isn't very clear exactly how, particularly as you change the RPC entry on the database. That is why most guides will say switch the DNS record across, because that is very easy to predict and do, rather than depending on Exchange "detecting" things have gone away or making modifications to the DAG configuration.


Author Comment

ID: 39672498

Thanks for your comment as always.
I had a chance to perform cross site failover (Primary site down scenario) and confirmed DNS  change was definitely required in my environment.
I've waited about an hour to complete the AD replication but Outlook didn't find CAS array automatically until DNS record was updated.


Author Comment

ID: 39684915
Good information was provided to my question.
Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article lists the top 5 free OST to PST Converter Tools. These tools save a lot of time for users when they want to convert OST to PST after their exchange server is no longer available or some other critical issue with exchange server or impor…
This article will help to fix the below error for MS Exchange server 2010 I. Out Of office not working II. Certificate error "name on the security certificate is invalid or does not match the name of the site" III. Make Internal URLs and External…
In this video we show how to create an email address policy in Exchange 2013. We show this process by using the Exchange Admin Center. Log into Exchange Admin Center.:  First we need to log into the Exchange Admin Center. Navigate to the Mail Flow…
A short tutorial showing how to set up an email signature in Outlook on the Web (previously known as OWA). For free email signatures designs, visit https://www.mail-signatures.com/articles/signature-templates/?sts=6651 If you want to manage em…
Suggested Courses

771 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question