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Old 10-04-2009, 08:24 AM   #1
SirSefu
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Registered: May 2007
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ssh connection timing out - Lenny out of the box


Dear All,

I'm having a hard time mastering this: I've just installed Debian Lenny into two new servers, and gone no further than installing OpenSSH-server (to accept remote ssh connections). My problem is that I'm getting network periodically hangs when I try to ssh from one of our remote-desktop-controlled "head" servers (Leopard Server 10.5.8). Here are the symptoms:

a) If I connect in ssh and start typing commands, there comes a point where I can no longer communicate new text through ssh. If I leave the terminal window open, I eventually get a message: "dRead from remote host server.ourdomain.com: Operation timed out
Connection to server.ourdomain.com closed."
b) Should I try immediately to connect, after a delay I get a message "ssh: connect to host server.ourdomain.com port 22: Operation timed out
c) Should I just connect to the server, not type any commands, and leave the connection open, I can come back even days later and be able to begin to send commands, but after a few the connection behaves like symptom a)

In all of the cases above, I can still ping the server I am trying to connect to.

Does the above seem familiar to anyone here, and could anyone tell me where to look (and what tools to use to do so)? Could this also be because of faulty DNS in the head server (I checked everything, as I had attributed new LAN IP's to the "sub servers" - but perhaps a mismatched MAC address?).

In any case, I'm really stumped, so if anyone can help, thank you very much.

PS: the "sub-servers" are Dell PE 1950's - there was an issue because of a "non-free" firmware (bnx2 for the gigabit ethernet card) not included in the default distribution, but normally I installed this just fine. Perhaps there is an issue there too?

Last edited by SirSefu; 10-04-2009 at 04:29 PM.
 
Old 10-04-2009, 04:29 PM   #2
SirSefu
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Registered: May 2007
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Any suggestions would be much appreciated. Thank you!
 
Old 10-07-2009, 11:26 PM   #3
SirSefu
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I don't think the problem has anything to do with the computer trying to connect to the sub-servers - the same thing happens when I try to ssh in from anywhere or any platform.
 
Old 10-08-2009, 03:39 AM   #4
donanap
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Registered: Sep 2008
Location: Perth, Australia
Distribution: RedHat, Solaris
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Smile SSH config file?

Hi,

Not sure how new you are to linux, so sorry if Im assuming something and you have already tried it! But..

Have you checked the ssh config file on the server?? Dont know where this file is on Debian - but RedHat its here:

Quote:
/etc/ssh/ssh_config
AND/OR
/etc/ssh/sshd_config
Make sure there is no connection timeout specified.

Good Luck,
Donanap
 
Old 12-17-2009, 07:41 AM   #5
yan_faubert
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Registered: Dec 2009
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Quote:
Originally Posted by SirSefu View Post
I don't think the problem has anything to do with the computer trying to connect to the sub-servers - the same thing happens when I try to ssh in from anywhere or any platform.
I had the same issue yesterday after installing lenny. Basically I could connect fine with ssh but as soon as I issued a command it would hang. ( I would start seeing some output and then it hung.)

When checking with 'netstat -an' I can see the socket was still 'ESTABLISHED'. I solved the problem by lowering my MTU value.

See this post.
http://www.snailbook.com/faq/mtu-mismatch.auto.html

I tried with mtu 576 and problem went away so I gradually bumped my MTU value until ping wouldn't work. I used this post to tune my MTU value:
http://www.debian.org/doc/manuals/de...ng_optimal_mtu


Hope this helps.
 
  


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