In previous versions of StoreFront such as 2.6 or older, Citrix recommended that you manually modify the hosts file on each StoreFront server to map the fully qualified domain name (FQDN) of the load balancer to the loopback address or the IP address of the specific StoreFront server. This ensures that Receiver for Web always communicates with the StoreFront services on the same server in a load balanced deployment. This is necessary because an HTTP session is created during the explicit login process between Receiver for Web and the authentication service and Receiver for Web communicates with StoreFront services using the base FQDN. If the base FQDN were to resolve to the load balancer, the load balancer could potentially send the traffic to a different StoreFront server in the group, leading to authentication failure. This does not bypass the load balancer except when Receiver for Web attempts to contact the Store service residing on the same server as itself. 

You can set loopback options using PowerShell. Enabling loopback negates the need to create host file entries on every StoreFront server in the server group. 

Example Receiver for Web web.config file:
<communication attempts="2" timeout="00:01:00" loopback="On" loopbackPortUsingHttp="80">

Example PowerShell command:
& "c:\program files\Citrix\receiver storefront\scripts\ImportModules.ps1"
Set-DSLoopback -SiteId 1 -VirtualPath "/Citrix/StoreWeb" -Loopback "OnUsingHttp" -LoopbackPortUsingHttp 81

Instructions

Refer to Citrix Documentation: Plan your StoreFront deployment - Load balancing