SPNego in Intranet and Form Based Authentication externally

Hi

Could anyone tell me if this activity is supported by Portal.

I have SPNego configured properly and it is running in my company network but user when he acess the same URL from Internet he is getting Page cannot be displayed. My requirement is to get Login screen where he can type user ID and password.

We cannot Provide different URL since requirement is to have a single URL.

Hope everyone understood the requirement.

Thanks