Code:
root@PRD /> rsh DR
KFAFH_DR: protocol failure due to unexpected closure from server end
root@PRD /> telnet DR
Trying...
Connected to DR.
Escape character is '^]'.
Connection closed.
root@PRD /> ftp DR
Connected to KFAFH_DR.
421 Service not available, remote server has closed connection
ftp> bye
root@PRD /> ssh 10.10.10.42
ssh_exchange_identification: Connection closed by remote host
root@PRD /> telnet 10.10.10.42
Trying...
Connected to 10.10.10.42.
Escape character is '^]'.#2 Suddenly couldn't connect
#3 After 1 hour, was able to telnet
How to identify the problem?