We have a salesforce community which is sitting on https://abc.force.com and we created a DNS CName record for custom domain help.mysite.com.
We followed the instructions as listed https://help.salesforce.com/HTViewSolution?id=000205653&language=en_US. The issue we are having is if we type http://help.mysite.com the redirect happens to https://abc.force.com/mycase/s but the domain name abc.force.com is not replaced with help.mysite.com

Please Help

How do I assign a custom domain when enabling Communities?  The Salesforce Help article states that it's possible but doesn't explain how and tech support hasn't been able to resolve it either.  I've gone to Domain Management>Domains and added a new domain (ex. community.company.com).  We've updated our domain controllers to include the appropriate CNAME records as required.  But when going to Customize>Communities>Settings and checking Enable Communities, it still forces you to select a domain that ends in ".force.com", not your custom domain.  We're building an external site which our company cannot include the ".force.com" ending.