Weird networking problem
From: Stig Bull (stig.bull.no.spam_at_broadpark.no)
Date: 04/18/05
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Date: Mon, 18 Apr 2005 11:05:30 +0200
We're experiencing som extremely weird networking problems at our
office, now I know this isn't a Sun related problem, but I'm trying this
group in order to get an idea of what to do next, or which forums/web
sites I really should direct my request at, since I haven't found any
dedicated, *good* networking forum while googing.
Here is the problem:
Last Friday morning, I was unable to SSH into the Sun servers at our
office. It worked as normal Thursday evening when we left so I thought
this was a Windows problem, but after rebooting the laptop as well as
another employee complained about the same problem, it turns out there's
something weird going on with out network.
What happens is this:
1: (Everything is on the same subnet, behind a Checkpoint firewall. The
switch is layer 2 so it doesn't route anything. No configuration has
been changed on the switch, the firewall, servers or office PC's)
2: We can SSH into 1 of 4 Sun servers
3: The same servers are reachable by FTP, ping and HTTP (not tried
anything else, Telnet is disabled), but not SSH
4: What turns up in var/adm/messages when we try SSH is this:
"Apr 18 10:04:29 jupiter sshd[15028]: [ID 800047 auth.crit] fatal:
Timeout before authentication for x.x.x.x" indicating that the packet
from the servers *seems* to be routed somewhere else
5: If we use SSH from our 3 remote production sites or even using a
remote PC with VPN, we can reach these servers
6: We can SSH from one server to the other between these 3, we can even
SSH into the fourth server from these 3, which is also reachable from
our office PC's, but SSH from this fourth server also times out to the
other 3
7: If I debug packets on the firewall, I can't see any SSH packets which
are routed elsewhere, so everything seems to be going on locally on the
switch/backbone, not going via the gateway at all
8: I've rebooted the switch twice, I even rebooted the servers *and* the
firewall and the problem still persists
9: I unplugged every cable from the switch one by one, while another
employee tried SSH into a server. SSH failed every single time
10: I replaced the switch this morning with an identical model and
configuration, but the problem still persists
11: On 2 of 3 servers I can sometimes get lucky and a SSH session is
successfully established -- after a looooong time. None of the other
employees gets a session established
12: SSH to the firewall and a Linux box which is on the same subnet
works perfectly
13: Just poking around I tried route -f on one of the servers. I was
able to SSH into it every single time, but still none of the other
employees were. Of course the gateway address disappeared with the route
flushed. After a reboot the server went back to "normal" and I was
unable to SSH into it again
14: This happens with SecureSSH (4.1/5.0), Putty and OpenSSH (various
versions) installed on servers.
So that's it, I've tried about everything I can think of, but use a
packet sniffer, even though I'm not sure if it will produce any results.
I do suspect this to be a routing issue even though I can't see any
'mal-routed' packets on the firewall.
Has anyone an idea of what I can try next, or perhaps provide me with a
link to some networking forum where I can ask about this?
--
Stig Bull
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