Debugging dropped shell connections over a VPN
Paul Keusemann
pkeusem at visi.com
Thu Jul 7 12:05:33 UTC 2011
Hello,
I am having problems with dropped shell connections over a VPN and I
need help diagnosing the problem.
My setup is something like this:
- My local network is a mix of AIX, HP-UX, Linux, FreeBSD and Solaris
machines running various OS versions.
- My gateway / firewall machine is running FreeBSD-8.1-RELEASE-p1
with ipfw, nat and racoon for the firewall and VPN.
The problem is that rlogin, ssh and telnet connections over the VPN get
dropped after some period of inactivity.
My initial thought was that the disconnect was being caused by an idle
timeout on the remote side of the VPN but I checked with the
administrator and that is not the case. The idle timeout is set to
something like 8 hours. The amount of idle time before a shell
connection is dropped seems to vary from less than five minutes to more
than half an hour more or less randomly or at best depending on
prevailing winds. It is difficult to determine exactly when the
connection is dropped because I don't know it has been dropped until I
try to type something into the remote shell and then I get an error
message and the connection is closed. The error message depends on the
type of connection:
rlogin: Read error from network: Connection reset by peer
ssh: Write failed: Broken pipe
telnet: Connection to ilt1000.eur.ad.sag closed by foreign host.
Running a script to generate output every 60 seconds on the remote shell
will keep the connection up most of the time but connections do get
dropped even with the script running.
I am pretty sure this is a VPN related issue. I have not had problems
with shell connections that don't go over the VPN. When my ISP still
had a UNIX shell host available, I used to leave shell sessions open to
it for weeks at a time. I have had these same problems with two
separate employers and three different remote VPN setups.
So, what I'm looking for is some way to figure out what the cause of the
disconnects is and a way to fix it. Any suggestions gladly accepted.
--
Paul Keusemann pkeusem at visi.com
4266 Joppa Court (952) 894-7805
Savage, MN 55378
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