UNIX for Advanced & Expert Users

Hi,

I am new to UNIX and I am given the responsibility of administering a UNIX machine recently. The system is a AIX 3.1 IBM. And, I am having problems in accessing the UNIX machine thru SSH.

All the users were able to logon to the Unix machine using SSH protocol earlier. But, I dont know what happened, one day it started giving the following error message when any user tried to login. " The host
is unreachable. The host may be down, or there may be a problem with the network connection. Sometimes, such problems may be caused by a misconfigured firewall." But this doesnt happen when I login thru putty/rlogin.


Can any one help me in identifying the problem and fixing . Any suggestions would be appreciated. Please be detail in your replies as I am new and dont understand UNIX terminology.

Thanx
pdepa.

ssh may not be running. try the command:
netstat -a | less
and look under listening for "ssh".
now ive never used aix before but it is a system V style unix ? if you have an /etc/rc.d directory look for a script called "ssh" , if you have that, starting, stopping, restarting ssh is as simple as:
/etc/rc.d/ssh [start | stop | restart]

if you dont have those scripts however, look for the sshd executable and start ssh manually. it would be /path/toexecutable/sshd ,
or from inside that directory, ./sshd