strange issue with ssh on F20 on DSL/VPN

[Ranjan Maitra]

So, I have a strange issue.

I have a local machine (laptop) connecting remotely to several desktops
including one that is a fully updated F20 (this is the one I have total
control over and therefore my choice of distributions). The others are
RHEL5's or Centos6. Connections are only permitted to all
machines through VPN (university policy). So, I on my new DSL
connection (which is wired and will replace my cable modem connection)
but currently both are active.  

Anyway, I can connect to all machines when I am on the cable modem
(using wireless) and VPN unlimited number of times. 

I can connect to all the non-F20 machines using ssh unlimited times
when I am on DSL and VPN.

However, I can only connect once t the F20 machine when I am on DSL and
the VPN. There is no way I can connect directly. (I can connect to one
of the non-F20 machines by ssh and from there connect to the F20 machine
however.) I can only connect directly again to the F20 machine by
ssh from my local machine by rebooting the remote F20 machine. And that
too for only one time. After I log out, I can not connect again.

What should I looking for? /var/log/secure does not have any entry when
I can not connect (however it does have an entry when I cancel the
connection by Ctrl-C -- "Connection closed").

Any suggestions as to how to diagnose and solve this problem?

Sorry for bringing forth the strangest of questions. I am hoping that
someone more familiar with networking issues will have some idea and
suggestions on what is going on.

Many thanks and best wishes,
Ranjan

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