GET Request using Host Header Value not IP Address

The beauty of the above iRule is that you may not have to modify AAM at all. By default SharePoint should set an AAM entry for the local machine's server name. Without making any modifications, client requests coming from the Internet that send a Host header that doesn't match this value will get redirected to this value (and subsequently break). So you could either modify AAM on each SharePoint server to match the external name of the application, or use an iRule on the F5 to change the Host header to what the SharePoint server expects.