I have 2 exchange servers (EXCH1 and EXCH2) that have Exchange 2013 on them. They are both on Windows Server 2012 R2 (Standard) machines. They are also a part of a DAG (Database Availability Group) (DAG1). Both servers are CAS (Client Access Server) and MAILBOX roles.

Currently, my router NAT settings are forwarding ports 25, 110, 80, and 443 to EXCH1. Would it be possible to port forward to DAG1 for these ports and let the Failover Cluster Manager decide which machine to use?

I tried Network Load Balancer, but it cannot co-exist with Failover Cluster Manager.


No, the DAG IP address is not a client access endpoint. You're on the right track by looking into load balancing, but NLB is also not a good choice (you've already discovered it's unsupported to use it on DAGs anyway).

So the solution for your scenario is to implement a load balancer. If Exchange is the only application you need to load balance, then I would look closely at a Kemp VLM.

  • Actually, around the time I posted the question, I decided to just have the router forward the packets to the IP address of the DAG. It actually forwards all of the email with no issues at all. The email clients still access one of the two IPs for each of the CAS, and it gets its email just fine.
    – Kevin
    Jul 26 '16 at 17:30
  • The DAG IP is not a client access endpoint. What you're doing might happen to work, but it's going to fail and perform badly in unpredictable ways that will cause problems for your users. Every customer that I've found who tried this had lots of problems with it. It's also not a supported configuration. Invest in a proper load balancer if you need high availability. Jul 28 '16 at 4:47

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