[Beowulf] ssh connection problem

Robert G. Brown rgb at phy.duke.edu
Tue May 29 13:27:37 PDT 2007

On Sun, 27 May 2007, Ruhollah Moussavi Baygi  wrote:

> Hi everybody at Beowulf,
> I have a serious problem with ssh connection to our cluster. Every
> hint/help/suggestion, which can help me to solve it, is highly appreciated.
> Most of the time, when users want to connect and run their programs from
> their own PCs, the ssh connection failed, especially during transfer files
> from/to head-node. Our user's PCs are mainly WindowsXP, so they use packages
> like SSH Secure Shell for connection and file transfer, or Putty for
> connection and WinSCP for file transfer.
> The error massage is as follows:
> 'Disconnecting: Corrupted MAC on input'

This sounds to me like hardware problems.  What does your physical
network look like?  Is it built with the right cables, within spec, with
decent switches?  Do you see other evidence of network packet

> <http://www.google.com/history/url?url=http://ubuntuforums.org/showthread.php%3Ft%3D202076&ei=wkJZRsGfHZf-0gTehKXrDQ&sig2=lIzQGYq3zN0Tz2EC8b4dAw&zx=JGkABbsjtaA&ct=w>
> or
> 'Disconnecting: bad packet

Yes, sounds like bad hardware.  Perhaps your cables aren't cat 5?
Perhaps your electrical power has noise?  Perhaps your switch(es) are
broken or have been taken over by trolls?  This sounds like you're
failing packet checksum tests or experiencing pretty serious TCP
collision problems.

What do the network statistics look like on the interfaces in question?


> length...<http://www.google.com/search?q=disconnecting:+bad+packet+length+from+windows+to+linux+machine&hl=en>',
> followed by a long integer.
> This problem has practically made our cluster unusable. So, I would be
> thankful for any coming advice.

Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu

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