ssh hangs with commands like 'ls -la', 'vi ...' etc.

ssh hangs with commands like 'ls -la', 'vi ...' etc.

Post by spate » Sun, 10 Feb 2002 23:07:26



I have a weird problem when accessing Suse linux machine from my work
network with ssh.  The problem is basically ssh session hangs when I
do simple commands like 'ls -al', 'vi ..', etc.  This only seems to be
a problem with Suse linux box.  I accessed the redhat linux box at
home from work and that works fine. No problem.  The funny thing is
that there is also no problem in accessing SuSe linux box while I am
on home network.  i.e I'm ssh'ing from one of the other windows box to
the SuSe linux box.

So, what is it about the network at work that causes the ssh hang
problem on SuSe linux box.

Thanks for any help

 
 
 

ssh hangs with commands like 'ls -la', 'vi ...' etc.

Post by David Efflan » Mon, 11 Feb 2002 05:28:07



Quote:> I have a weird problem when accessing Suse linux machine from my work
> network with ssh.  The problem is basically ssh session hangs when I
> do simple commands like 'ls -al', 'vi ..', etc.  This only seems to be
> a problem with Suse linux box.  I accessed the redhat linux box at
> home from work and that works fine. No problem.  The funny thing is
> that there is also no problem in accessing SuSe linux box while I am
> on home network.  i.e I'm ssh'ing from one of the other windows box to
> the SuSe linux box.

> So, what is it about the network at work that causes the ssh hang
> problem on SuSe linux box.

I have no trouble ssh to SuSE 7.3 at home from work (Putty or ssh) on a
roundabout path through 56K frame relay to California, out adsl.pacbell,
in adsl.ameritech to my SuSE firewall/masq/router in Illinois.  Maybe it
is a packet mismatch issue (fragmenting).

I am using SuSEfirewall2 with ssh hosts restricted by hosts.allow/deny.

What is the path into your home network (are both on a router or is one of
them the router)?  You should make sure that the mtu for LAN nics is set
at or below your external connection.  Pppoe has an 8 byte header so to
get through the 1500 ethernet, so the max mtu for pppoe is 1492.  Your
internal nics should be set at or below that.  Some souces suggest mtu
1452 or even 1412 (to allow for VPN), but I have had no trouble using
1492.  The nic for pppoe should be 1500.

If it is connected by regular modem, the norm for mtu now seems to be
1524, so outside modem connections would not normally be a problem.

--
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ssh hangs with commands like 'ls -la', 'vi ...' etc.

Post by spate » Tue, 12 Feb 2002 02:20:53




> > I have a weird problem when accessing Suse linux machine from my work
> > network with ssh.  The problem is basically ssh session hangs when I
> > do simple commands like 'ls -al', 'vi ..', etc.  This only seems to be
> > a problem with Suse linux box.  I accessed the redhat linux box at
> > home from work and that works fine. No problem.  The funny thing is
> > that there is also no problem in accessing SuSe linux box while I am
> > on home network.  i.e I'm ssh'ing from one of the other windows box to
> > the SuSe linux box.

> > So, what is it about the network at work that causes the ssh hang
> > problem on SuSe linux box.

> I have no trouble ssh to SuSE 7.3 at home from work (Putty or ssh) on a
> roundabout path through 56K frame relay to California, out adsl.pacbell,
> in adsl.ameritech to my SuSE firewall/masq/router in Illinois.  Maybe it
> is a packet mismatch issue (fragmenting).

> I am using SuSEfirewall2 with ssh hosts restricted by hosts.allow/deny.

> What is the path into your home network (are both on a router or is one of
> them the router)?  You should make sure that the mtu for LAN nics is set
> at or below your external connection.  Pppoe has an 8 byte header so to
> get through the 1500 ethernet, so the max mtu for pppoe is 1492.  Your
> internal nics should be set at or below that.  Some souces suggest mtu
> 1452 or even 1412 (to allow for VPN), but I have had no trouble using
> 1492.  The nic for pppoe should be 1500.

> If it is connected by regular modem, the norm for mtu now seems to be
> 1524, so outside modem connections would not normally be a problem.

All my machines are basically behind router.  And only way in is
through ssh (port 22). The mtu is set to 1500 on suse and redhat box.
So, what you are suggesting is to change the mtu set on suse to 1492.
Is that correct.  By the way just to make it clear, I can ssh from my
win2k(laptop) machine home to suse 7.3 and everything works fine.  Its
from work with the same win2k(laptop) machine that the ssh hangs on
commands like 'ls -al', or vi, etc.  Thanks for any suggestion.
 
 
 

ssh hangs with commands like 'ls -la', 'vi ...' etc.

Post by spate » Wed, 13 Feb 2002 02:47:47





> > > I have a weird problem when accessing Suse linux machine from my work
> > > network with ssh.  The problem is basically ssh session hangs when I
> > > do simple commands like 'ls -al', 'vi ..', etc.  This only seems to be
> > > a problem with Suse linux box.  I accessed the redhat linux box at
> > > home from work and that works fine. No problem.  The funny thing is
> > > that there is also no problem in accessing SuSe linux box while I am
> > > on home network.  i.e I'm ssh'ing from one of the other windows box to
> > > the SuSe linux box.

> > > So, what is it about the network at work that causes the ssh hang
> > > problem on SuSe linux box.

> > I have no trouble ssh to SuSE 7.3 at home from work (Putty or ssh) on a
> > roundabout path through 56K frame relay to California, out adsl.pacbell,
> > in adsl.ameritech to my SuSE firewall/masq/router in Illinois.  Maybe it
> > is a packet mismatch issue (fragmenting).

> > I am using SuSEfirewall2 with ssh hosts restricted by hosts.allow/deny.

> > What is the path into your home network (are both on a router or is one of
> > them the router)?  You should make sure that the mtu for LAN nics is set
> > at or below your external connection.  Pppoe has an 8 byte header so to
> > get through the 1500 ethernet, so the max mtu for pppoe is 1492.  Your
> > internal nics should be set at or below that.  Some souces suggest mtu
> > 1452 or even 1412 (to allow for VPN), but I have had no trouble using
> > 1492.  The nic for pppoe should be 1500.

> > If it is connected by regular modem, the norm for mtu now seems to be
> > 1524, so outside modem connections would not normally be a problem.

> All my machines are basically behind router.  And only way in is
> through ssh (port 22). The mtu is set to 1500 on suse and redhat box.
> So, what you are suggesting is to change the mtu set on suse to 1492.
> Is that correct.  By the way just to make it clear, I can ssh from my
> win2k(laptop) machine home to suse 7.3 and everything works fine.  Its
> from work with the same win2k(laptop) machine that the ssh hangs on
> commands like 'ls -al', or vi, etc.  Thanks for any suggestion.

There is little more info that I have now.  The 'ls -al' command will
be successfull if the output is just few lines(3 or 4).  If the output
happens to be say a page or so long.  Then the ssh client will hang.
This is also true with commands like 'cat ', etc.  It seems like the
amount of data that's coming back also has something to do with this.

Thanks again.

 
 
 

1. ssh hangs on commands like 'ls -al', 'vi'

I have a weird problem when accessing Suse linux machine from my work
network with ssh.  The problem is basically ssh session hangs when I
do simple commands like 'ls -al', 'vi ..', etc.  This only seems to be
a problem with Suse linux box.  I accessed the redhat linux box at
home from work and that works fine. No problem.  The funny thing is
that there is also no problem in accessing SuSe linux box while I am
on home network.  i.e I'm ssh'ing from one of the other windows box to
the SuSe linux box.

So, what is it about the network at work that causes the ssh hang
problem on SuSe linux box.

Thanks for any help.

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