Exchange 2013 DNS for internal and external domain

Question

Hi All,
I have been assigned a task to implement Microsoft Exchange Server 2013. I need some help in setting up DNS namespaces and design a strategy to have same internal and external names. Let me share some details here.
We have an Active Directory domain myinternaldomain.net, and we have a public domain
mypublicdomain.com and we have setup email policy to have
mypublicdomain.com as the SMTP domain for all the users. We have created another DNS zone in Active directory integrated DNS and created a records for
mail.mypublicdomain.com and autodiscover.mypublicdomain.com which will point to CAS NLB IP. We have 2 CAS servers and 2 MBX servers, we have configured DAG for MBX High availability and planning to implement WNLB for CAS as
hardware LB is out of scope due to budget constrains.
We want to have same URLs for OWA, Autodiscover, ECP and other services from internal network as well as from public network. Users should not be bothered to remember two URLs, using one from internal and other from public networks. I also want to confirm
that with this setup in place do i need to have myinternaldomain.net and server names in SAN certificate?
Thanks

Answer 1

Hi Sccmnb,
You can easily achieve this using split DNS.
Internal DNS hostname "mail.mypublicdomain.com" will be pointing to your internal CAS NLB IP and the external public DNS hostname"mail.mypublicdomain.com" will be pointing to the Network device or
Reverse proxy server IP.
Depending upon users access location(internal\external) the IPs would vary and they should be able to access the website with same name.
The names that you would require on the certificate(Use EAC or powershell to raise the request) for client connectivity would be
SN= mail.mypublicdomain.com
SAN= autodiscover.mypublicdomain.com
You don't need to have the active directory domain name present in the certificate.
Additional  to this you need to update the AutodiscoverURI for all servers and OWA,ECP,Autodiscover Virtual Directories InternalURL and ExternalURL fields with appropiate public names.
Some additional Info:
*Internal vs. External Namespaces
Since the release of Exchange 2007, the recommendation is to deploy a split-brain DNS infrastructure for the Internet-based client namespaces. A split-brain DNS infrastructure enables different IP addresses to be returned for a given namespace
based on where the client resides – if the client is within the internal network, the IP address of the internal load balancer is returned; if the client is external, the IP address of the external gateway/firewall is returned.
This approach simplifies the end-user experience – users only have to know a single namespace (e.g., mail.contoso.com) to access their data, regardless of where they are connecting. A split-brain DNS infrastructure, also simplifies the configuration of Client
Access server virtual directories, as the InternalURL and ExternalURL values within the environment can be the same value.
*Managing Certificates in Exchange Server 2013 (Part 2)
*Nice step by step article
Designing a simple namespace for Exchange 2013
Regards,
Satyajit
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