On 02/20/2018 09:33 AM, H wrote:
> On 02/19/2018 10:09 PM, Marcelo Ricardo Leitner wrote:
>> On Mon, Feb 12, 2018 at 08:05:18PM -0500, H wrote:
>> ...
>>> Not sure if I am reading your reply correctly but I should clarify
>>> that I have problems when running naked ssh to the server, when I
>>> run ssh to the same server but over the VPN connection (that goes
>>> via third server) everything is flawless.
>>>
>>> I should also explain that:
>>>
>>> - I am on a workstation (located in the US), ssh-ing into server 1
>>> (located in the US).
>>>
>>> - From server 1 I use scp to transfer large files from server 2
>>> (located in Europe) to server 1 (in the US).
>>>
>>> The above randomly disconnects.
>> You have two ssh sessions here. AFAICT, it's the first one
>> (workstation->server 1) that randomly disconnects, right?
>>
>>> However, when:
>>>
>>> - I use a VPN connection to server 3 (also located in Europe).
>>>
>>> - From the same workstation as above, do exactly as above,
>>> connections are rock-solid.
>> It would seem to me that something between your workstation and server
>> 1 is possibly mishandling TCP options (being it sack, timestamps or
>> both). Is there a router or a firewall in between?
>>
>> Try doing a traffic capture between both and see why it hangs. If
>> you're hesitant to post the binary traffic capture, post the text
>> version of it with anonymized IP addresses. Just please be sure to
>> disable ssh protocol so it would include TCP details on it then.
>>
>> Marcelo
> Let's reduce the problem to a simpler case: the workstation running CentOS 7 is behind a router, behind the same router is the server running CentOS 6. For various reasons, I access the server via its external IP address, not the local one. Access is via ssh.
>
> When using straight ssh, the connection times out after random times, always less than 20 minutes or so, though, with the error message "packet_write_wait: broken pipe", not the common "write failed: broken pipe".
>
> However, when I am in a ssh session on a VPN connection (which terminates in an outside server far away from my network), the ssh connection does /not/ time out.
>
> Further, accessing the same server as first mentioned, in the identical fashion, from another computer running CentOS 6, I never encounter the "packet_write_wait" error and disconnection.
>
> My conclusion is thus that this is not a router issue but could conceivable be a bug in CentOS 7. I am also ruling out a cable issue or a physical network card issue since the VPN connection is stable.
>
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