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Next: RFS: scitools
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External
Since: Aug 26, 2009
Posts: 4
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(Msg. 1) Posted: Wed Aug 26, 2009 11:21 am
Post subject: ssh problem
Archived from groups: linux>debian>isp (more info?)
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hi all,
having a problem since a few months and i cant really figure it out.
i have a debian machine standing in China and i connect from Europe, so
going over there just for this is slightly cumbersome.
i did have some driver issues in the past but after replacing the
network cards it worked fine.
At the moment:
i can login using SSH and issue commands.
but when opening a file or starting top the screen goes black until the
connection times out, reset by peer.
i can copy files to the machine using SCP but i can not copy them back,
it stalls until the time out.
a website is hosted on the machine and you can connect to it but it
keeps on waiting for the server till the morning comes.
the machines acts as a router for a local LAN, eth1 faces the LAN and
eth0 faces the net, no problems for the people on the LAN
not sure what it is but my first suspect would be the firewall/routing,
i use shorewall.
so, before i try disabling the firewall etc... to see if it has any
results and risk losing the working LAN part of the story i wonder if
somebody here has a clue on what it could be.
Thanks anyways,
Randall
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External
Since: Aug 26, 2009
Posts: 4
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(Msg. 2) Posted: Wed Aug 26, 2009 11:21 am
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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randall wrote:
> hi all,
>
> having a problem since a few months and i cant really figure it out.
>
> i have a debian machine standing in China and i connect from Europe, so
> going over there just for this is slightly cumbersome.
>
> i did have some driver issues in the past but after replacing the
> network cards it worked fine.
>
> At the moment:
> i can login using SSH and issue commands.
> but when opening a file or starting top the screen goes black until the
> connection times out, reset by peer.
>
> i can copy files to the machine using SCP but i can not copy them back,
> it stalls until the time out.
>
> a website is hosted on the machine and you can connect to it but it
> keeps on waiting for the server till the morning comes.
>
> the machines acts as a router for a local LAN, eth1 faces the LAN and
> eth0 faces the net, no problems for the people on the LAN
>
> not sure what it is but my first suspect would be the firewall/routing,
> i use shorewall.
>
> so, before i try disabling the firewall etc... to see if it has any
> results and risk losing the working LAN part of the story i wonder if
> somebody here has a clue on what it could be.
>
> Thanks anyways,
>
> Randall
>
sorry, wrong list.
but if anybody has some idea its not forbidden to respond anyway.
apologies
Randall
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External
Since: Aug 14, 2009
Posts: 3
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(Msg. 3) Posted: Wed Aug 26, 2009 11:21 am
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Hi,
On Wed, Aug 26, 2009 at 04:52:38PM +0200, randall wrote:
> i can login using SSH and issue commands.
> but when opening a file or starting top the screen goes black until the
> connection times out, reset by peer.
>
> i can copy files to the machine using SCP but i can not copy them back,
> it stalls until the time out.
>
> a website is hosted on the machine and you can connect to it but it
> keeps on waiting for the server till the morning comes.
>
> the machines acts as a router for a local LAN, eth1 faces the LAN and
> eth0 faces the net, no problems for the people on the LAN
Looks like a PMTU issue.
Would you happen to have net.ipv4.ip_no_pmtu_disc = 1 in your sysctls?
--
Bertrand Yvain
http://www.lost-oasis.fr/
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External
Since: Aug 26, 2009
Posts: 4
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(Msg. 4) Posted: Wed Aug 26, 2009 11:21 am
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Bertrand Yvain wrote:
> Hi,
>
> On Wed, Aug 26, 2009 at 04:52:38PM +0200, randall wrote:
>> i can login using SSH and issue commands.
>> but when opening a file or starting top the screen goes black until the
>> connection times out, reset by peer.
>>
>> i can copy files to the machine using SCP but i can not copy them back,
>> it stalls until the time out.
>>
>> a website is hosted on the machine and you can connect to it but it
>> keeps on waiting for the server till the morning comes.
>>
>> the machines acts as a router for a local LAN, eth1 faces the LAN and
>> eth0 faces the net, no problems for the people on the LAN
>
> Looks like a PMTU issue.
> Would you happen to have net.ipv4.ip_no_pmtu_disc = 1 in your sysctls?
>
just noticed that i do can cat small files, it hangs on more substantial
sized files though.
but below answers the question, nope.
host:~# cat /etc/sysctl.conf
#
# /etc/sysctl.conf - Configuration file for setting system variables
# See sysctl.conf (5) for information.
#
#kernel.domainname = example.com
#net/ipv4/icmp_echo_ignore_broadcasts=1
# Uncomment the following to stop low-level messages on console
#kernel.printk = 4 4 1 7
##############################################################3
# Functions previously found in netbase
#
# Uncomment the next line to enable Spoof protection (reverse-path filter)
#net.ipv4.conf.default.rp_filter=1
# Uncomment the next line to enable TCP/IP SYN cookies
#net.ipv4.tcp_syncookies=1
# Uncomment the next line to enable packet forwarding for IPv4
#net.ipv4.conf.default.forwarding=1
# Uncomment the next line to enable packet forwarding for IPv6
#net.ipv6.conf.default.forwarding=1
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External
Since: Aug 14, 2009
Posts: 3
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(Msg. 5) Posted: Wed Aug 26, 2009 11:21 am
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Wed, Aug 26, 2009 at 05:12:36PM +0200, randall wrote:
> Bertrand Yvain wrote:
> > Looks like a PMTU issue.
> > Would you happen to have net.ipv4.ip_no_pmtu_disc = 1 in your sysctls?
> >
> but below answers the question, nope.
The resource might be set by something else. You can check the actual
value like this:
# /sbin/sysctl net.ipv4.ip_no_pmtu_disc
If it's still 0, my guess stays on MTU.
> just noticed that i do can cat small files, it hangs on more substantial
> sized files though.
I guess that "small" is around your MTU on eth0. Should be 1500 for
regular ethernet, but there might be an encapsulation layer somewhere...
You should try lowering it to something safe:
# ifconfig eth0 mtu 1280
This will most probably fix your problem. Then you'll have to
investigate why the default MTU is not good for your network and what
should be the max allowed value.
--
Bertrand Yvain
http://www.lost-oasis.fr/
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External
Since: Aug 26, 2009
Posts: 4
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(Msg. 6) Posted: Wed Aug 26, 2009 11:21 am
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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randall wrote:
> Bertrand Yvain wrote:
>> On Wed, Aug 26, 2009 at 05:12:36PM +0200, randall wrote:
>>> Bertrand Yvain wrote:
>>>> Looks like a PMTU issue.
>>>> Would you happen to have net.ipv4.ip_no_pmtu_disc = 1 in your sysctls?
>>>>
>>> but below answers the question, nope.
>> The resource might be set by something else. You can check the actual
>> value like this:
>>
>> # /sbin/sysctl net.ipv4.ip_no_pmtu_disc
>>
>> If it's still 0, my guess stays on MTU.
>
host:~# sysctl net.ipv4.ip_no_pmtu_disc
net.ipv4.ip_no_pmtu_disc = 0
>
setting ifconfig eth0 mtu 1280
does seem to help and solves the immediate problem, i have a working
connection again. Thanks 
not sure what i did to ***** this up, actually no idea what the MTU
actually does apart from what i read on google the last ten minutes.
>
>
>
>
>
>>> just noticed that i do can cat small files, it hangs on more substantial
>>> sized files though.
>> I guess that "small" is around your MTU on eth0. Should be 1500 for
>> regular ethernet, but there might be an encapsulation layer somewhere...
>>
>> You should try lowering it to something safe:
>>
>> # ifconfig eth0 mtu 1280
>>
>> This will most probably fix your problem. Then you'll have to
>> investigate why the default MTU is not good for your network and what
>> should be the max allowed value.
>>
>
>
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External
Since: Dec 26, 2008
Posts: 3
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(Msg. 7) Posted: Sat Aug 29, 2009 9:20 am
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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hi,
I've read all the responses to this email, but it is still unclear to me if described behavior could be the result of a damaged ethernet cable. The logic would be that smaller packets have higher chances of getting through, both on initial send event and when re-sending non-ACKed packets. I could be totally wrong here, so that is why I'm asking.
I had recently deteriorating link quality to my server, which manifested itself as rising (on the scale of dozens of hours) percentage of lost packets when running mtr or ping from my server to some external server. This had finally led to complete loss of connectivity. I did get higher link reliability by decreasing link speed to 10MBps, I haven't tried MTU though. Link was fixed by tech support doing something either to the patch-panel or a patch-cord between the server and patch-panel.
> hi all,
>
> having a problem since a few months and i cant really figure it out.
>
> i have a debian machine standing in China and i connect from Europe, so
> going over there just for this is slightly cumbersome.
>
> i did have some driver issues in the past but after replacing the
> network cards it worked fine.
>
> At the moment:
> i can login using SSH and issue commands.
> but when opening a file or starting top the screen goes black until the
> connection times out, reset by peer.
>
> i can copy files to the machine using SCP but i can not copy them back,
> it stalls until the time out.
>
> a website is hosted on the machine and you can connect to it but it
> keeps on waiting for the server till the morning comes.
>
> the machines acts as a router for a local LAN, eth1 faces the LAN and
> eth0 faces the net, no problems for the people on the LAN
>
> not sure what it is but my first suspect would be the firewall/routing,
> i use shorewall.
>
> so, before i try disabling the firewall etc... to see if it has any
> results and risk losing the working LAN part of the story i wonder if
> somebody here has a clue on what it could be.
>
> Thanks anyways,
>
> Randall
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External
Since: Aug 29, 2009
Posts: 1
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(Msg. 8) Posted: Sat Aug 29, 2009 1:20 pm
Post subject: Re: ssh problem [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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Just a thought
I had a similar issue in the past.
I connect to several servers over ssh from my ubuntu 8.10 machine.
Servers were debian 4, opensuse and ubuntu 8.04. The ssh connection
would freeze if I issued a long ls command "ls -l /etc" for example.
cat a big text file. Editing with vi was an almost sure freeze. Guess
what. I tried windows and putty to connect and no freezes. So I think
"ssh client problem?" I try messing with lots of ssh_config options
and no success, I try to run putty over wine and FREEZE! I found no
solution but to reboot to windows and use putty. Eventually it stopped
freezing without a reason. I now use ubuntu 9.04 as desktop but it
stopped freezing while still using ubuntu 8.10. I really don't know
what was happening that time.
2009/8/29 Bogdan <do.IT.DeleteThis@i.ua>:
> hi,
>
> I've read all the responses to this email, but it is still unclear to me if described behavior could be the result of a damaged ethernet cable. The logic would be that smaller packets have higher chances of getting through, both on initial send event and when re-sending non-ACKed packets. I could be totally wrong here, so that is why I'm asking.
>
> I had recently deteriorating link quality to my server, which manifested itself as rising (on the scale of dozens of hours) percentage of lost packets when running mtr or ping from my server to some external server. This had finally led to complete loss of connectivity. I did get higher link reliability by decreasing link speed to 10MBps, I haven't tried MTU though. Link was fixed by tech support doing something either to the patch-panel or a patch-cord between the server and patch-panel.
>
>
>> hi all,
>>
>> having a problem since a few months and i cant really figure it out.
>>
>> i have a debian machine standing in China and i connect from Europe, so
>> going over there just for this is slightly cumbersome.
>>
>> i did have some driver issues in the past but after replacing the
>> network cards it worked fine.
>>
>> At the moment:
>> i can login using SSH and issue commands.
>> but when opening a file or starting top the screen goes black until the
>> connection times out, reset by peer.
>>
>> i can copy files to the machine using SCP but i can not copy them back,
>> it stalls until the time out.
>>
>> a website is hosted on the machine and you can connect to it but it
>> keeps on waiting for the server till the morning comes.
>>
>> the machines acts as a router for a local LAN, eth1 faces the LAN and
>> eth0 faces the net, no problems for the people on the LAN
>>
>> not sure what it is but my first suspect would be the firewall/routing,
>> i use shorewall.
>>
>> so, before i try disabling the firewall etc... to see if it has any
>> results and risk losing the working LAN part of the story i wonder if
>> somebody here has a clue on what it could be.
>>
>> Thanks anyways,
>>
>> Randall
>
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>
>
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