IIS 10 and host headers?

Windows 2016 - IIS 10  I'm inexperienced with using host headers.  Our developers have an app that logs the ip's making a request.  They've explained that they're seeing the gateway address of the server, instead of the public address being logged.  Is this the normal behavior when using host headers, or should the public address be logged?  The xxx is indeed the servers gateway address, not a single public ip address is being logged.  If the public ip address should be logged.  What might I have mis-configured?  The internal users of the site have their ip address being logged correctly.  Thanks

C:\Program Files (x86)\Log Parser 2.2>logparser "select c-ip, count (c-ip) as requestcount from u_ex200206.log group by c-ip order by count(c-ip) desc"
c-ip          requestcount
------------- ------------
xxx.xxx.xxx.xxx  584795