ssh login delays

[Bob Hartung]

Hi all,
   I have two linux boxes at home: FC3 and FC4.  I am logging into the 
FC4 box from FC3 and the time from issuing the 'ssh ....' command until 
I see the password prompt is 36 seconds.  As I am new to this I have no 
idea where to begin looking for the cause of the delay.

I can login into the FC4 box from my wife's OS X Mac with virtually 
no delay.

Pointers please on where to begin looking for the hangup.

TIA

Bob

[Andy Green]

On Monday 05 September 2005 04:22, Bob Hartung wrote:
> Pointers please on where to begin looking for the hangup.

When you're scratching your head about what is happening on the wire, tcpdump 
is always a good place to start.  Run it in another command prompt and try 
the bad connect, see what packets are going where.

DNS problems are a popular cause of long network delays.

If nothing shows in tcpdump, try the connect again with ssh -v -v -v and see 
what the last happenings are before the delay.

Check your logs on the server side (/var/log/messages I guess).

-Andy

[Tom Mitchell]

On Sun, Sep 04, 2005 at 11:22:41PM -0400, Bob Hartung wrote:
> Date: Sun, 04 Sep 2005 23:22:41 -0400
> From: Bob Hartung 
> To: fedora-list 
> Subject: ssh login delays
> Reply-To: For users of Fedora Core releases
>
> Hi all,
>   I have two linux boxes at home: FC3 and FC4.  I am logging into the 
> FC4 box from FC3 and the time from issuing the 'ssh ....' command until 
> I see the password prompt is 36 seconds.  As I am new to this I have no 
> idea where to begin looking for the cause of the delay.
>
> I can login into the FC4 box from my wife's OS X Mac with virtually 
> no delay.
>
> Pointers please on where to begin looking for the hangup.

Compare and contrast:

ssh -x user@host
    ssh -X user@host

My guess is that the systems are establishing an secure tunnel/ channel
for X11 traffic.   The other very common time consumer is host name lookup
both forward and backward (DNS bind).    If I recall correctly the ssh 
config files (/etc/ssh/*) changed between FC3 and FC4 on some of this.

You can check the the X11 thing by starting xterm and then inspect $DISPLAY.
If $DISPLAY is a "localhost:11.0" something address there is an SSH tunnel...

[J. K. Cliburn]

I found quite by accident one evening when my ISP was unavailable that
sshd (or perhaps ssh -- can't quite remember which) was performing a
DNS lookup of a nonexistent host _kerberos.<FQDN>.  This turned out to
be because the GSSAPIAuthentication flag was set to yes in the
ssh[d]_config file.  You might try setting that flag to no (or
commenting it out altogether).  That solved my slow ssh login
response.

Jay

On 11/15/05, Nifty Hat Mitch  wrote:
> On Sun, Sep 04, 2005 at 11:22:41PM -0400, Bob Hartung wrote:
> > Date: Sun, 04 Sep 2005 23:22:41 -0400
> > From: Bob Hartung 
> > To: fedora-list 
> > Subject: ssh login delays
> > Reply-To: For users of Fedora Core releases
> >
> > Hi all,
> >   I have two linux boxes at home: FC3 and FC4.  I am logging into the
> > FC4 box from FC3 and the time from issuing the 'ssh ....' command until
> > I see the password prompt is 36 seconds.  As I am new to this I have no
> > idea where to begin looking for the cause of the delay.
> >
> > I can login into the FC4 box from my wife's OS X Mac with virtually
> > no delay.
> >
> > Pointers please on where to begin looking for the hangup.
>
> Compare and contrast:
>     ssh -x user@host
>     ssh -X user@host
>
> My guess is that the systems are establishing an secure tunnel/ channel
> for X11 traffic.   The other very common time consumer is host name lookup
> both forward and backward (DNS bind).    If I recall correctly the ssh
> config files (/etc/ssh/*) changed between FC3 and FC4 on some of this.
>
> You can check the the X11 thing by starting xterm and then inspect $DISPLAY.
> If $DISPLAY is a "localhost:11.0" something address there is an SSH tunnel...
>
> --
>         T o m  M i t c h e l l
>         Found me a new place to hang my hat :-)
>         Found me a cable too.
>
> --
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