check network connectivity 
check correct ipaddress
ping ipaddress

'who' or 'w'  is the command used to find the users who 
logged in the system and their attempts, with the help of 
some options

Failed ssh logs are either written in /var/log/messages, or
/var/log/secure (configurable in /etc/syslog.conf). I am
assuming that the failed login attempts are recorded in
/var/log/secure:

 grep ' authentication failure' /var/log/secure | sed -e
's/^\(.*\)\(rhost.*\)$/\2/p' | tr -s " " | cut -f2 -d"=" |
cut -f1 -d" " | sort -n | uniq -c

Will show you the count, and the IP/hostname of machines
that tried to access the system via ssh

The command is ,

cat /var/log/messages | grep "Failed password"

it will show all the user which is not able to login.