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Exchange high availability namespace design and planning

An Exchange Server is already up and running in the organization. Before installing a second Exchange Server, it’s good to go to the drawing board. Exchange high availability namespace design and planning is by far the most crucial task. Take your time, and write the topology before deploying. In this article, you will learn about Exchange high availability namespace design and planning configuration.

Information Exchange high availability namespace design

Before you start, look at the install Exchange Server course and install the first Exchange Server. You will have a clear understanding of how to install, configure, and maintain Exchange Server.

When installing Exchange Server on-premises, it doesn’t matter which version, this can be Exchange 2010/2013/2016/2019, the internal URLs match the fully qualified domain name (FQDN) of the Exchange Server. This design is by default. Examples how internal hostname look like are .local, .lan, or .internal.

You are asking for trouble if you proceed like this, for example:

  • You can’t buy a third-party certificate based on the internal FQDN URLs.
  • Autodiscover certificate warnings and issues when connecting with clients.
  • You can’t load balance between multiple Exchange Servers with an internal FDQN.
  • Adding another Exchange Server in the environment will give problems.
  • Configuring Exchange hybrid deployment will give problems.

We recommend making use of a generic namespace. For example,

We have an internal domain named exoip.local and an external domain In my example, we will configure the namespace

Exchange high availability namespace planning

An architecture view of Exchange high availability namespace is shown below in the topology.

  • The public DNS / External DNS will have a record that resolves to the firewall or router’s public IP address. It will then NAT any external connections to the load balancer internal IP.
  • The Internal DNS zone will have a record that resolves to the load balancer internal IP address.
Exchange high availability namespace design and planning architecture

Configure Kemp load balancer

Install and configure Kemp load balancer with an IP address. After that, add both the Exchange Servers to the load balancer for HTTPS high availability.

Configure internal DNS Exchange Server

Configure the DNS zones internally with Pinpoint DNS. Both the records that we are going to add will look like the following.

Record Type   DNS Name                 Internal IP Address
-----------   --------                 -------------------

Read the article Configure internal DNS Exchange Server.

Configure internal and external URL in Exchange Server

We will configure the internal and external URLs with the same name. Almost all the URLs will have the in the configuration. That’s because the AutoDiscover URL will be different.

Service                  Internal and External URL
-------                  -------------------------
Exchange Control Panel
Exchange Web Services
Exchange ActiveSync
Offline Address Book
Outlook Web App
Outlook Anywhere

Read the article Configure Internal and External URL in Exchange Server.

Configure external DNS Exchange Server

There are six records that we are going to add to the public DNS. These are the A record, CNAME record, and MX record. The MX record will have 4 records for high availability.

Record Type    TTL    DNS Name                 Priority   Value
-----------    ---    --------                 --------   -----
A              300             
CNAME          300    
MX             300    @                        10
MX             300    @                        20
MX             300    @                        30
MX             300    @                        40

Read the article Configure external DNS Exchange Server.

This article is part of the course Exchange Server high availability.


In this article, you learned about Exchange high availability namespace design and planning best practices. This is a setup for multiple Exchange Servers in a single site. Please pay close attention to the namespace design and plan it accordingly to avoid problems later on.

Did you enjoy this article? You may also like Load Exchange Management Shell in PowerShell ISE. Don’t forget to follow us and share this article.



ALI TAJRAN is a passionate IT Architect, IT Consultant, and Microsoft Certified Trainer. He started Information Technology at a very young age, and his goal is to teach and inspire others. Read more »

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