[CentOS] how to debug ssh slow connection issues.

Fri May 23 18:34:33 UTC 2008
Paul Heinlein <heinlein at madboa.com>

On Fri, 23 May 2008, Jason Pyeron wrote:

>>> debug3: Normalising mapped IPv4 in IPv6 address
>>> debug3: Trying to reverse map address
>>> paused 7 seconds
>> Here, obviously, is part of the problem. Your name service isn't 
>> answering reverse lookups for your LAN addresses -- or it least it 
>> isn't answering them in a timely manner. Fixing that, either 
>> through DNS or /etc/hosts, will help a bunch.
> [root at ~]# date && host  && date && host
> host80.1.internal.pdinc.us && date Fri May 23 13:55:52 EDT 2008
> domain name pointer host80.1.internal.pdinc.us.
> Fri May 23 13:55:52 EDT 2008
> host80.1.internal.pdinc.us has address Fri May 23 13:55:52 EDT
> 2008
> [root at ~]#
> Hmmm, does not take 7 seconds.

User-space utilities like /usr/bin/host don't always provide an 
accurate reflection of the name services inherited by init- or 
kernel-launched processes -- especially if the network wasn't (for 
reasons unknown) fully functional at boot time.

Do you remember if there were any network timeouts when you booted the 
machine in question?

Are you running nscd?

I'm still inclined to believe that hostname-lookup issues are involved 
here; an strace with timestamps might provide a better glimpse of the 
exact system calls that are timing out.

Paul Heinlein <> heinlein at madboa.com <> http://www.madboa.com/