one of the reason is -we will get this error in most of the cases it reaches maximum allowed space on Unix box.but still Unix administrator can login because they will have diff login shell which is not in host level max allowed level,so check with Unix team to clear some space to login to the server.
second possible reason is that host is not available in network
Third reason could be server you are trying to connect is in DMZ zones.to connect server in dmz zone first you need to login to dmz server and switch from the dmz server to the host you want to connect.
below command can be used to connect from dmz to destination server
$ssh -h <DestinationHostname>
(or )
$ssh -h <DestinationHostname> su - username
second possible reason is that host is not available in network
Third reason could be server you are trying to connect is in DMZ zones.to connect server in dmz zone first you need to login to dmz server and switch from the dmz server to the host you want to connect.
below command can be used to connect from dmz to destination server
$ssh -h <DestinationHostname>
(or )
$ssh -h <DestinationHostname> su - username
