External SharePoint login issues

Im setting up an external facing SharePoint site for some of our partners to have access to and Im having an issue with logging in. What I found out is that if I go to developers.companyxyz.com I get the login prompt, when I enter my credentials its sending me to the default page in SharePoint which is http://servername/Pages/Default.aspx

How do I stop it from redirecting to the internal URL and make it stay at developers.companyxyz.com?