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Hello i have CentOS installed on vmware , few days ago every thing was working fine. today every time im connect with putty to the CentOs server after few minutes it disconnect me , how can i find what is the reason ?

when i check /var/log/secure im getting :

Jan 23 18:01:09 localhost sshd[17461]: Exiting on signal 15 when i check the "/var/log/messages" there is nothing that says something about this signal my iptables is closed

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Try to see if the connection remains up when you connect from/to the same machine but using a different router. –  Gaia Nov 7 '12 at 13:24

2 Answers 2

Add the following line to the /etc/ssh/ssh_config file:

ServerAliveInterval 60

The number is the amount of seconds before the server with send the no-op code.

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well i did it then restarted the server checked to see if sshd is up with netstat -tulpn , and i see its listening , but now i can't even connect to the server . also stoped the iptables –  user61104 May 2 '11 at 10:54
    
You shouldn't have to restart the server after changes to /etc/ssh/ssh_config, it's the configuration for the client. Are you sure you edited ssh_config instead of sshd_config? –  Eduardo Ivanec May 2 '11 at 10:59
    
ha ok , yeah i edit the ssh_config in the end of the file –  user61104 May 2 '11 at 11:01
    
The ssh_config file would be if you're sshing from Linux. The matching setting in putty is on the Connection screen, Seconds between keepalives –  DerfK May 2 '11 at 11:43
    
i updated my question –  user61104 May 2 '11 at 13:47

A signal 15 in the log indicates something more serious then just a timeout issue.

I would run strace -p PID for the sshd process and see why it's actually dieing.

You should also try ssh from the server to localhost and see if that's stable. For example: ssh root@0

Definitely you should install any available CentOS upgrades as well. If the problems persist, then try reinstall the SSH server package in case it's been compromised or corrupted somehow.

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