Unable to connect to server using its name using “Connect-VIServer ” command

wrote the following PowerCLI command inside my powercli version 5.5 to connect to a server by its name :-

Connect-VIServer-Server"t***.v****ces.intra"-User root -Password"*****"

but I got the following error:-

Connect-VIServer:07/08/201513:11:54   Connect-VIServer   Could not resolve the requested VC server.ConnectionException+FullyQualifiedErrorId:Client20_ConnectivityServiceImpl_Reconnect_NameR esolutionFailure,VMware.VimAutomation.ViCore.Cmdlets.Commands.ConnectVISer ver

now if I replace the server name with the server IP the command will work well. so can anyone advice why I am unable to connect to server by its name?