Disclaimer: I do not have a Z system, so I'm going to ignore everything
about it other than reboot/IPL which, to my limited mind, mean similar
things enough that I'll just probably say "reboot" and hope you can help
me cover the gap there. :-)

First, nice reporting of the issue. I appreciate the time it took you to
write all of that, and think through it, and fight through SRs, etc.

On to the problem, I think I agree with each of you a bit; clearly some
packets are reaching your system, so the network outside of the system is
working correct to get the packets there. To get more information
regarding what is happening on the wire from this machine's perspective I
would recommend using tcpdump:

sudo zypper install tcpdump  #in case it is not installed already
sudo /usr/sbin/tcpdump -n -s 0 -i any port 22
While that is running, go ahead and try to SSH in from some other system
that does not work. If you can do it from a system that does work, that
may be useful too. What we should see are packets going back and forth,
rather than just going one-way. tcpdump is neat because it works before
the Linux firewall (Netfilter) interferes, so even if it is blocked by the
host's firewall (you said it is not) the packets should show up.

Another test we may be able to do is get more output from SSH during the
connection. If you have a Linux box that CANNOT SSH in, then use that
one; just add '-vvv' (three 'v' characters) to get a ton of debugging
information from the client (passwords and keys are never shown as I recall):

ssh -vvv username@remote.box.goes.here
Some other useful information for us may be ip and routing information,
which is simple to get:

ip a  #ip address info
ip r  #routing information
ip neigh  #arp/neighbor information
In this case I m mostly interested in the address and routing information,
as I wonder if there may be a route missing to allow packets to get back
to the source properly. Do you have other systems, SLES 11 maybe, that
can be SSH'd-info, from which we can get the same commands' output? It
could be useful for comparison purposes if nothing else.

Good luck.

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