Sitios internos - Problema

[edmarinho]

Tengo varios sitios internos.
No puedo accederlos de una oficina remota.
Muéstrame las seguiente mensajes.

The requested URL could not be retrieved
While trying to retrieve the URL: http://sitios_interno
The following error was encountered:
Unable to determine IP address from host name for sitios_interno
The dnsserver returned:
Name Error: The domain name does not exist
This means that:
The cache was not able to resolve the hostname presented in the URL.
Check if the address is correct

Que tengo que hace?