SSH terminal locking up from OS X to FreeBSD

Doug Hardie bc979 at
Wed Feb 23 06:19:25 GMT 2005

On Feb 22, 2005, at 13:50, jim at wrote:

> * Eric F Crist <ecrist at> [2005-02-22 15:35:53 
> -0600]:
>> On Feb 22, 2005, at 3:11 PM, jim at wrote:
>> What version of Mac OS X are you using?  All of my workstations are 
>> Mac
>> OS X, and all but one server (an old cobalt raq 2) are running FreeBSD
>> 5.3, and I have never seen a problem with using ssh from a terminal to
>> a FreeBSD system.
> OS X is always the latest, currently 10.3.8.
> I have no control over the version this
> particular FreeBSD system, but this problem has
> persisted for several versions of Mac OS X and
> FreeBSD.

I have been using ssh from my Macs to FreeBSD versions from 2.5 and up. 
  Currently I have servers running 4.6 and 5.3.  My connections stay 
active for one hour without problems.  The one hour limit is from an 
undocumented feature in Apple's Airport that terminates a connection if 
there is no activity for an hour.  The configuration on both ends is 
out of the box except that I force version 2 on both machines and have 
changed the port away from 22.

To see what is happening using tcpdump do the following on both 
machines as root:

1. tcpdump -xXs1500 port 22 > xxx   (xxx is some file name to save the 
trace) the connection and cause it to fail
3. terminate the tcpdumps.
4. The traces in the xxx files will be time stamped and you should be 
able to check them side by side and watch what happens.  One or the 
other will probably stop responding.

Another thing that may help is to use (as root) ktrace on the sshd 
server and on the ssh client.  That will generate a lot of output but 
may help with the tcpdump to see why the problem is occuring.

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