If you've deployed Exchange in a production environment you've undoubtedly gone through the joy of figuring out what you were going to do for load balancing. This really became relevant in Exchange 2007 when adoption for Outlook Anywhere or RPC over HTTPS started picking up steam. This was also when ActiveSync really started taking off as everyone started jumping on the iPhone craze (whatever happened to those devices anyway?).
So, what do you do for load balancing? You have a few choices. There are software solutions such as Windows NLB, which is ok for small environments, but even Microsoft says to go with a more robust load balancing solution. And to be completely honest, it's not the easiest thing to get going in a virtual environment (see VMware KB article here for more info: http://kb.vmware.com/kb/1006580). You have (or had...read this: http://blogs.technet.com/b/server-cloud/archive/2012/09/12/important-changes-to-forefront-product-roadmaps.aspx) Forefront Thread Management Gateway which can load-balance traffic to your Exchange CAS servers, but TMG itself is not load balanced, unless you deploy Windows NLB.
Then there are dedicated load balancer solutions such as those from Kemp, F5 and many other vendors. These come in two flavors; virtual and physical appliances. If you already have physical load balancers then, no sweat, you are golden (but keep readin and watch the video just for the heck of it). If not, and you desire something slightly better than Windows NLB, my recommendation is to take a look at the virtual appliance load balancers available today. Most of the major vendors who have previously sold only hardware solutions have caught onto the cost effectiveness and ease of support that comes with a virtual appliance based solution. Other vendors only deal in the virtual appliance space. In either case, it's a great place to start.
On the topic of virtual appliance load balancing solutions, I get to the point of this article. VMware vCloud Networking and Security, the networking and security suite for VMware's cloud solutions, provides a great load balancing solution through vCNS Edge. Edge is deployed as a virtual appliance, comes in three sizes based on your requirements (i.e. number of client sessions), and can be deployed in a highly available configuration. From a load balancing perspective it provides everything that Exchange 2013 requires in the way of load balancing and more. Take a look at the video for a quick tutorial on configuring vCNS Edge for Exchange load balancing, then check out the links below for more information on vCNS Edge.
-alex
http://www.vmware.com/products/datacenter-virtualization/vcloud-network-security/overview.html
http://blogs.vmware.com/vsphere/tag/vshield-edge