Exchange email access resilience using DNS round robin ?

People,

I'm trying to implement email resiliency solution internally and also externally with no Load Balancer access, so I came up with the below Idea:

http://www.tutorius.com/setting-up-a-dns-round-robin-in-windows
http://exchange929.blogspot.com.au/2013/10/high-availability-for-exchange-2013-cas.html

which I will be applying for all of my Exchange Server 2013 Std. Edition running CAS role:

Internally
AutoDiscover.domain.com points to CAS server 1 internal IP address on AD Site 1
OWA.domain.com points to CAS server 1 internal IP address on AD Site 1

AutoDiscover.domain.com points to CAS server 2 internal IP address on AD Site 2
OWA.domain.com points to CAS server 2 internal IP address on AD Site 2

...

AutoDiscover.domain.com points to CAS server N internal IP address on AD Site N
OWA.domain.com points to CAS server N internal IP address on AD Site N

and also Externally
AutoDiscover.domain.com points to CAS server 1 public IP address on the internet.
OWA.domain.com points to CAS server 1 public IP address on the internet.

AutoDiscover.domain.com points to CAS server 2 public  IP address on the internet.
OWA.domain.com points to CAS server 2 public  IP address on the internet.

...

AutoDiscover.domain.com points to CAS server N public IP address on the internet.
OWA.domain.com points to CAS server N public  IP address on the internet.

I know how to add those entries since both DNS servers are using Windows, but how do I set the TTL to just 15 seconds for the OWA and AUtodiscover entries only?

What's the impact if I reduce the TTL on the forward lookup zones which impact all domain.com lookup ?

Thanks in advance,
LVL 13
Senior IT System EngineerSenior Systems EngineerAsked:
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Mino DCSolution ConsultantCommented:
Try using this:
https://freeloadbalancer.com/

Instead of DNS RR

Works very well.

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AmitIT ArchitectCommented:
You cannot archive the same result, what you get with HLB. DNS RR is not application aware solution. Until your server is not down, DNS RR will be sending the traffic to failed server. Better go for HLB.
Senior IT System EngineerSenior Systems EngineerAuthor Commented:
OK, but in this case, if I want to achieve "some sort" of site resiliency, can I still use the DNS round-robin with the above approach?
Senior IT System EngineerSenior Systems EngineerAuthor Commented:
Thanks !
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