ADFS 2.2 Internet explorer login prompt for external users

Hey All,

I am testing a setup with 2 ADFS 2.2 Server 2012 R2.

ADFS1

ADFS2

named adfs.myCompany.com

I have the servers published via a reverse proxy/load balancer (hardware) and the endpoint

https://adfs.myCompany.com/adfs/ls/IdpInitiatedSignon.aspx , is reachable. There is an external DNS entry NAT'd via a firewall rule.

Now, this is strange, when i am outside the network, as in non domain joined, and I use chrome or firefox, I get a form to authenticate on. That is great, but internet explorer pops up a login dialog box.

This is not an expected behaviour. Is this becuase I am not using the web proxy role on seperate boxes, or have i missed something in my configuration.regards,

Rob

Rob