They usually have to be on the same physical network.
Have you made sure they have IP addresses in the same subnet assigned to them?
*****
If you think my answer has helped - please provide me with a Kudos rating and mark as Helpful Answer!!
I do not work for Virgin Media - all opinions expressed are of my own and all answers are provided from my own and past experiences.
Office 365, Dynamics CRM and Cloud Computing Jedi