SSL Certificates on multiple interface IPs

We have performed a Nessus scan on our network and all the interfaces of our core router have failed on the SSL cert scan on port 443. I can easily request and import a certificate from our internal CA on one of the interfaces and it is fine. But with multiple routing interfaces, how do i either use that same cert for all interfaces or generate multiple certificates (one per interface) if it only supports 2 certificates?

Thanks