Random Disconnects with Direct SSH Connection BUT Not Through Intermediary?!?!

This is a strange problem that has been slowly getting worse over
about 5 months. I'm curious if anyone has had a similar experience or
can give me some pointers to trouble shooting ... or at least
"assigning the blame".

When I'm at work I maintain an ssh connection from my work Win2K
machine to my Linux home machine. I use this to backup work data and
to access my email. Ever since I got the work DSL account to do this
I get random disconnects (Putty reports:Network error: software caused
connection abort) after any where from 5min to 60 min, lately it is
typically closer to 5 min. BUT, if I connect from work to an
intermediate host then to my home system it will maintain the
connection for a whole day. I always disconnect at the end of the
day. I've tried another free MSWin ssh client (www.ssh.com) and it
behaves the same way.

The only common factor I can see is that my home and work connections
are through the same ISP but the intermediate host is on a totally
separate network. In Canada the "national" phone company (Bell) also
offers ISP services. The residential ISP is Sympatico and the
business ISP is BellNet. These are the connections I use. The
intermediate host I use is www.klug.on.ca. At one point I remember
reading about gamers and voice-chatters having issues connecting
directly to each other inside the Sympatico network but no solutions
were provided.

The home system is on 24/7 and I monitor the pppoe connection ... it
is relatively stable. I can keep the same IP address for weeks at a
time. The work connection is not monitored as closely but as far as
IP assignment goes it is at least stable through the day.

Any pointers, opinions, links or solutions would be appreciated. :-)

--
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On Fri, 03 Feb 2006 11:00:57 -0500, Doug Mitton wrote:

> I get random disconnects (Putty reports:Network error: software caused
> connection abort) after any where from 5min to 60 min,

I think first you should repeat your normal direct SSH usage using another
SSH client other than Putty and see if it disconnects as well. This way we
can remove your SSH client from the troubleshooting equation.

--
Nick DePetrillo
Network Security Engineer
OSHEAN
PGP Key: http://pgp.mit.edu:11371/pks/lookup?...rch=0x121245B5

Nicholas DePetrillo <(E-Mail Removed)> wrote:

>On Fri, 03 Feb 2006 11:00:57 -0500, Doug Mitton wrote:
>
>> I get random disconnects (Putty reports:Network error: software caused
>> connection abort) after any where from 5min to 60 min,
>
>I think first you should repeat your normal direct SSH usage using another
>SSH client other than Putty and see if it disconnects as well. This way we
>can remove your SSH client from the troubleshooting equation.

> connection for a whole day. I always disconnect at the end of the
> day. I've tried another free MSWin ssh client (www.ssh.com) and it
> behaves the same way.

I've tried this one with the same symptoms. I'm as sure as I can be
at this point that its not the ssh client. Free clients for MSWin are
rare.
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Doug Mitton <(E-Mail Removed)> wrote:

>When I'm at work I maintain an ssh connection from my work Win2K
>machine to my Linux home machine. I use this to backup work data and
>to access my email. Ever since I got the work DSL account to do this
>I get random disconnects (Putty reports:Network error: software caused
>connection abort) after any where from 5min to 60 min, lately it is
>typically closer to 5 min. BUT, if I connect from work to an
>intermediate host then to my home system it will maintain the
>connection for a whole day. I always disconnect at the end of the
>day. I've tried another free MSWin ssh client (www.ssh.com) and it
>behaves the same way.

>(snipped)

>Any pointers, opinions, links or solutions would be appreciated. :-)

Well, I have finally managed to resolve this issue.

The main problem is the "poor" quality of my DSL connection BUT to
work around it I had to do the following:

1) My firewall rules. Due to the constant attacks on my ssh server I
added rules to only allow 3 connection attempts per minute. When DSL
was bad this was being exceeded and disconnecting me. To resolve I
moved my ssh server to an alternate port with much more reasonable
(connection attempt rate) firewall rules.

I still run my server on the standard port as well BUT severely
restricted access with firewall rules ... just to keep the script
kiddies entertained.

2) My sshd server. While I was using KeepAlive in both my client and
server configurations I WAS NOT using ClientAliveInterval in my
sshd_config file, so the connection was timing out VERY quickly during
my "poor" DSL performance times.

Hopefully, some else may find this information useful.
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