"We selected Loadbalancer.org for our virtualized Exchange 2010 cluster deployment a year ago. Since then the virtual load balancers have been performing flawlessly. Support is always very speedy in responding to questions. The sales staff has been very helpful as well. Overall we are very happy with our choice, and will gladly recommend them to other customers looking for a similar solution."
Kurt Tavares
City of Tracy
Microsoft Exchange Server, the mainstay of Microsoft’s Unified Communications solution has grown beyond being regarded as the standard in business email into a fully fledged communications tool.
Once difficult to manage at scale, the Microsoft Exchange platform has reached a level of maturity. With a simplified architecture, it has evolved to support high availability and scalability by design.
To implement highly available and scalable deployments of Microsoft Exchange Server, Microsoft recommends using a load balancer to distribute the traffic among multiple Exchange servers. Both current and legacy versions of Exchange support load balancing, with a different approach and recommendations dependant on the version you are running.
Example Exchange 2016 deployment using a minimal 2 server setup.
| Protocol | Role | Ports | Load balancing methods |
|---|---|---|---|
| TCP | CAS | 443 | Used for Outlook on the Web, AutoDiscovery, Web Services, ActiveSync, Outlook Anywhere, Offline Address Book, Exchange Administration Center). Layer 4 DR (Direct Routing – Ultra-fast, local server based load balancing) Layer 7 SNAT |
| TCP | CAS | 25 | Used for Inbound SMTP Layer 4 DR (Direct Routing – Ultra-fast, local server based load balancing) Layer 7 SNAT (Flexible, URL switching and cookie insertion capabilities) |
| TCP | CAS | 110, 995 143,993 |
Used for POP3 clients Used for IMAP4 clients Layer 4 DR (Direct Routing – Ultra-fast, local server based load balancing) Layer 7 SNAT (Flexible, URL switching and cookie insertion capabilities) |
| Protocol | Role | Ports | Load balancing methods |
|---|---|---|---|
| TCP | CAS | 80 | Layer 7 SNAT |
| TCP | CAS | 443 | Layer 7 SNAT |
| TCP | HT | 25 | Used for the HT (Hub Transport) role Layer 4 DR (Direct Routing – Ultra-fast, local server based load balancing) Layer 4 NAT (Fast Load balancing throughput) Layer 7 SNAT (Flexible, URL switching and cookie insertion capabilities) |
| TCP | CAS | 110, 995, 143, 993, 135, 60201 |
Used for POP3 clients Used for IMAP4 clients RPC endpoint mapper Static port for Exchange address book service Layer 7 SNAT |
In Exchange 2010, key functionality is split into 3 roles: Mailbox Server, Client Access Server and Hub Transport Server. In Exchange 2013, roles were consolidated into Client Access Server and Mailbox Server. In Exchange 2016, primary functionality was consolidated into a single role – the Mailbox Server. For all versions of Exchange, the load balancer is used to load balance all required client connection protocols, as well as inbound SMTP connections.
For Exchange 2013 & 2016, all sessions to the CAS servers are stateless and therefore persistence/affinity is no longer required on the load balancer. For Exchange 2010, some protocols require affinity and others don’t as detailed here.
The load balancer fully supports SSL termination and backend server re-encryption. SSL offloading for Exchange 2013 and later is supported from 2013 SP1 as detailed here. However, for scalability and effective load sharing we recommend terminating SSL on the Exchange Servers rather than on the load balancer.
For a detailed look at deploying across multiple data centers, please refer to this blog.
Eliminate stress with the totally unrestricted Enterprise MAX. Licensed for unlimited clusters and back-end servers, this load balancer offers the ultimate combination of price, performance and scalability. In fact, it's so good many of our most demanding customers have been running on this platform for years, without requiring an upgrade.
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