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Situation: I am trying to connect from OpenSSH client inbuilt with Git Bash running on Windows 7 professional x64 to OpenSSH server that runs on Ubuntu Server LTS 14 x64. Both of which are over the same local network, that is monitored by Cyberoam.

Also I need to mention that the server installation is fresh and for now I am the only one who is trying to connect to the system.

Problems:

  • Out of 100 tries to connect from client, hardly 5 attempts are successful, and the rest are rejected by server, i.e. I cannot connect to the server from client, in normal process.
  • Sometime right after successful long in, I get disconnected from server, I do not think it is the problem with time out.

Ideal solution: I should be able to connect to from client to server for each single attempt. Server should not refuse the connection.

More details:

  • If I run run the SSH command from client in debug mode, I get:

$ ssh -vvv 192.168.0.120 OpenSSH_6.6.1, OpenSSL 1.0.1i 6 Aug 2014 debug2: ssh_connect: needpriv 0 debug1: Connecting to 192.168.0.120 [192.168.0.120] port 22. debug1: connect to address 192.168.0.120 port 22: Connection refused ssh: connect to host 192.168.0.120 port 22: Bad file number This is not the only message I get, sometimes at the end of the list, there is an error from the server.

  • SSH is running over the default port, 22.
  • If I use PortQry.exe to test the port and IP accessibility, I get no issue.

$ portqry -n 192.168.0.120 -e 22 Querying target system called: 192.168.0.120 Attempting to resolve IP address to a name... Failed to resolve IP address to name querying... TCP port 22 (ssh service): LISTENING

  • As mentioned the connection is gone though a a phycal firewall called Cyberoam, that has been newly reconfigured and all the problems started since then.
  • I have checked /var/log/auth.log, but there is no entry for remote access via SSH from client machine.
  • I have already set the keys on client and server, and I can log in with out password.
  • I can ssh to server itself with no issues.
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  • As mentioned the connection is gone though a a phycal firewall called Cyberoam, that has been newly reconfigured and all the problems started since then. that sounds like you already isolated the problem and know where to start looking further. Check the firewall config. Commented Mar 7, 2015 at 8:23
  • @HBruijn: The issue is that, the firewall is under the administration of IT technician and he says that he has not done anything to cause this, I do not have access to that part, or I can solidly state that THIS IS THE PROBLEM Commented Mar 7, 2015 at 8:35

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Something like this where the problem is intermittent, and (by your own description) caused by a firewall, I would immediately look at IPS. Ask your network admin to disable the Intrusion Prevention Service for 22/tcp to 192.168.0.120.

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  • Intrusion Prevention Service is disabled on the inter connection network Commented Mar 7, 2015 at 11:59

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