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DNS Round Robin

Domenic DiPasquale
Domenic DiPasquale asked
Does anyone know of a Domain Service Providers that support DNS Round Robin, or if it's even possible? I would like to setup a Round Robin configuration that points to two IP addresses that my exchange servers are using. In case one goes down, that other exchange server will handle the workload. Note, the only traffic that will be going across the two IP addresses is HTTPS traffic, I'm using a 3rd IP address for mail flow / spam filtering. If this is not a recommended configuration, could you recommended another solution on how I can accomplish this. Thank you for your time.
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Seth SimmonsSr. Systems Administrator
what version of exchange?
some places will have their own 3rd party load balancer (F5, netscaler, etc.) which will take in all traffic and distribute between multiple servers (CAS in this case) internally

you could do a CAS array depending on the exchange version or just use windows NLB

Load balancing
Senior Solution Architect
Most Valuable Expert 2015
Top Expert 2015
If you are trying to load balance CAS roles WNLB is not recommended for Production environments. Layer 7 load balancer is required for E2007 or E2010 (you can get by with a layer 4 load balancer but you will need to use multiple namespaces for health monitoring), which is not as clean.

If you are using E2013 Layer 4 is do-able but Layer 7 is always better.

CAS Array is used for Exchange 2010 only and by itself is not a load balancing mechanism, you still need a load balancer.

DNS Round Robin is not true load balancing, although it goes back and forth between each IP, if one IP is not reachable the clients that are connected to the IP that is no longer reachable clients will not fail over to the other IP. Their DNS caching will need to expire or (ipconfig /flushdns) before it will detect the other IP. Not a preferred method for CAS.

Domenic DiPasqualeSystems Administrator II


The version I'm using is Exchange Server 2013 Standard on both servers. I'm more concerned about fail over than load balancing. Will a layer X load balance appliance / server allow me to utilize fail over?