In a common scenario, you have two ways to load balance MS Exchange FE:
1 – DNS with Round Robin;
2 – Network load balancing.

The DNS RR approach is the easiest and cheapest way to load balance a web server (Exchange FE).
Configuring Round Robin in DNS is as simple as assigning multiple (in this case 2) ip addresses to a unic Fully Qualified Domain Name.
In this case the balancing is done by the DNS server which will answer every request with a different IP address.
This solution only requires you to configure your DNS infrastructure to be able to load balance those Exchange FE.

If you want/need a more robust solution than go for Network Load Balancing.
For NLB you need an additional network card in each server and to configure NLB. NLB is a Windows server 2k3 and over service that monitor the availability and load to distribute the load over each node of the cluster.

For a more in depth and detailed instruction on both scenarios please read this article.

Regards,