issue with openssh-server running in a libvirt based centos virtual machine

[Nico Kadel-Garcia]

On Fri, Jan 26, 2018 at 2:50 PM, Adrian Pascalau
<adrian27oradea at gmail.com> wrote:
> On Fri, Jan 26, 2018 at 5:02 AM, Darren Tucker <dtucker at dtucker.net> wrote:
>> On 26 January 2018 at 06:44, Adrian Pascalau <adrian27oradea at gmail.com>
>> wrote:
>>>
>>> [...]
>>> debug1: SSH2_MSG_KEXINIT sent [preauth]
>>>
>>> Here the debug mode stops, and there is no login prompt shown on the
>>> Putty window.
>>
>>
>> This behaviour is often caused by a path MTU/fragmentation problem.
>>
>> If you run "netstat" on both client and server and find the SSH TCP
>> connection you should see a "Send-Q" column.  This column is the number of
>> bytes in the TCP socket buffer that the other end has not acknowledged.  If
>> it is non-zero number that remains above zero or increases then IP
>> fragmentation is likely your problem and you need to fix whatever in your
>> environment is causing that.
>
> Darren, thanks for your reply.
>
> In the ssh client side, I have a windows host that runs Putty. So I
> installed a new centos to be able to see the "Send-Q" column, since
> the windows netstat does not have it. Surprise, the ssh connection
> works like a charm. I went back to the windows box to try again with
> Putty, and I have the same issue. So could this be because of windows?
> I cannot suspect Putty, since I tried this with another windows based
> ssh client (MobaXterm), and the same issue happens.

As much as I love Putty as a well-built tool, it's gotten a bit long
in the tooth. May I suggest that you test it from a Cygwin shell on
your client host?