You have just finished installing Windows Server 2012/R2. You have assigned the server a name and finished configuring IP addresses. You have tested your configuration by using ping to verify network connectivity with your default gateway and another server on the network, and everything worked fine. However, the next day, a colleague tells you that when he tried to ping the server, his request timed out. You try to ping your colleague's computer and receive a reply just fine. Why can't your colleague ping your server successfully?