I'm using Windows Authentication on two separate websites, on the same server, with the same domain postfix. Both are using https with two certificates. The problem is that when external users visit both sites, they are prompted for credentials twice even though the credentials will be exactly the same.
I've tried disabling Anonymous Authentication on both sites. External users will not be using machine connected to the domain, so I can't add the sites to any sort of intranet zone.
Is there anything I can change to allow each site to accept the authentication cookie from a related site??