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Date:      Tue, 12 Jun 2018 18:28:45 -0700
From:      "Ronald F. Guilmette" <rfg@tristatelogic.com>
To:        freebsd-questions@freebsd.org
Subject:   NIC locks up for no reason (?)
Message-ID:  <23524.1528853325@segfault.tristatelogic.com>

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I am experiencing a really rather odd problem, and could use some
helpful advice.  I'm sure there is a good explanation for why this
is happening, but at the moment I have no idea what it is.

More than a month ago, I got myself a shiny new VM on one of the
many providers of such on the Internet.  I loaded up 11.1-RELEASE-p9,
fiddled sshd so that it would run on a somewehat obscure unused port.

Anyway, after doing the above things, all was running well, and exactly
as expected for some time thereafter.  (I have mostly just been using
the box for some obscure research purposes.)

I never set up any kind of filewall on the thing because frankly,
I was doing so little with the box I didn't think I'd need one.

Recently, I decided to install and run apache24, which I did.
I configured that also to run on a non-standard port, since my
intent was that the web stuff it would be serving up would only
be stuff that I and perhaps a few close friends would look it.
Apache started up just fine, and I was able to acces web content
on the box via the non-standard port, from a system elsewhere on the
Internet.  No problem.

Anyway, now it appears that the NIC on this VM system is effectively
locking up from time to time, and I have no idea how to even begin
to debug this problem.  This happened a few days ago, and I managed
to get to a virtual console, I logged in as root, and then I rebooted
FreeBSD on the VM and again, all was well... for awhile.

When this problem occurred before, it appeared that the (virtual) NIC
of the VM was not accepting -any- packets from outside.

Now the NIC has locked up again.  Once again, from the outside it
appears that it isn't responding to pings. or to traceroutes, or to
ssh (on my non-standard port), or to attempts to telnet to the
(non-standard) HTTP port I'm using.

Traceroutes -out- from the VM also get absolutely nowhere... not even
one hop.  Pings rom the VM to its own (externally routable) IPv4
address work fine.

I logged in again via the virtual console and once again, just like
the last time this happened (a couple of days ago), I can see nothing
obviously wrong.  There's plenty of free disk space, and top is showing
the CPU as being >95% idle.

ifconfig output looks perfectly normal to me... the interface in
question is listed as "UP".

Whet the devil could be wrong?

The relevant hosting company has assured me that they haven't been doing
anything new or special lately.

The Handbook says that (recent vintage) FreeBSD provides three different
flavors of firewalls.  Are any of these three enabled by default?  What
about TCP Wrapper?  Is that enabled by default on an out-of-the-box
install of 11.1-RELEASE?

What else could possibly explain a NIC periodically becoming totally
unresponsive...  at least from the outside... apparently just because
I had the audacity to install and run apache24?



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