ssh session automatically closing

hattori.hanzo · 01-19-2009, 09:50 PM

We have encountered a very strange issue with OpenSSH on CentOS 5.2 (openssh-server-4.3p2-26.el5_2.1). On one of our hosts, the ssh sessions are being closed automatically for no apparent reason with the following message:

Quote:

Read from remote host server.com: Connection reset by peer
Connection to server.com closed.

If we try and reconnect we get

Quote:

ssh: connect to host server.com port 22: Connection refused

If we check the port, it shows its closed

Quote:

PORT STATE SERVICE
22/tcp closed ssh

We have checked the following:

iptables is stopped
hosts.allow - no entries
hosts.deny - no entries
erased openssh
re-installed openssh (used default sshd_config)

The port appears to close for like 5 mins, then re-opens again.

All the previous sessions then remains open on the system.

Quote:

03:40:24 up 1:19, 4 users, load average: 0.17, 0.05, 0.01
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
root pts/0 server2.com 02:41 56:02 0.01s 0.01s -bash
root pts/1 server2.com 02:25 53:13 0.00s 0.00s -bash
root pts/2 server2.com 03:07 11:56 0.01s 0.01s -bash
root pts/3 server2.com 03:40 0.00s 0.01s 0.00s w

We have run out of ideas and might rebuild the box soon.

regards

anomie · 01-19-2009, 10:07 PM

I've seen some (not all) of this behavior when I am sitting behind a NAT device, accessing a remote host. After a certain idle period, I get disconnected - but the ssh session is still active on the host.

Try setting ServerAliveInterval 90 in ~/.ssh/config on the client side for the user you're running as. For more details, see the manpages for ssh_config(5).

hattori.hanzo · 01-19-2009, 11:31 PM

Thanks for responding. I tried that but still no go...

The hosts are on the same switch so there is no nat'ing involved.

regards

anomie · 01-20-2009, 01:45 PM

Ouch. Well, what do /var/log/secure and /var/log/messages (on the server side) have to say when the sshd connection is getting disrupted?

jstephens84 · 01-20-2009, 02:43 PM

I kind of had this problem. Mine was due to when setting up the httpd I got interupted and placed an extra 255 in the subnet. I would connect but then it would disconnect for no reason after 5 or 10 minutes. Some times right in the middle of an edit. Does this happen on all your clients or only one?

hattori.hanzo · 01-22-2009, 12:18 AM

We finally found out the cause.

It was a conflicting IP address on the network which was causing the ssh disconnects.

Thank you for all your help and suggestions.

regards

mewto · 06-16-2010, 02:35 PM

I have exactly the same problem. When I saw this final resolution, I don't think that could be our problem. Well, as it turned out that I have exactly the same problem with IP conflict. A Windows admin put a new server in. The only way he check is use ping. Since this is a public facing server, I made it not ping-able. He just grab it without even checking the DNS, or the asset record. Where is the process?

There you have it. Simple solution for a puzzling problem.

raseeler · 01-12-2012, 01:12 AM

I had somewhat similar situation like this, it was because of the following line in /etc/pam.d/sshd ,
session required /lib/security/pam_limits.so

Whenever i try to log in as root, it gets connected, suddenly closes the session. After removing this line, problem solved