From owner-freebsd-questions Mon Jun 15 23:10:47 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id XAA27162 for freebsd-questions-outgoing; Mon, 15 Jun 1998 23:10:47 -0700 (PDT) (envelope-from owner-freebsd-questions@FreeBSD.ORG) Received: from freefall.freebsd.org (freefall.FreeBSD.ORG [204.216.27.21]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id XAA27136 for ; Mon, 15 Jun 1998 23:10:39 -0700 (PDT) (envelope-from kuku@gilberto.physik.RWTH-Aachen.DE) Received: from gilberto.physik.RWTH-Aachen.DE (gilberto.physik.rwth-aachen.de [137.226.30.2]) by freefall.freebsd.org (8.8.8/8.8.5) with ESMTP id XAA23101 for ; Mon, 15 Jun 1998 23:09:46 -0700 (PDT) Received: (from kuku@localhost) by gilberto.physik.RWTH-Aachen.DE (8.8.8/8.8.7) id IAA02723; Tue, 16 Jun 1998 08:10:40 +0200 (MEST) (envelope-from kuku) Message-ID: <19980616081040.53544@gil.physik.rwth-aachen.de> Date: Tue, 16 Jun 1998 08:10:40 +0200 From: Christoph Kukulies To: Doug White Cc: Christoph Kukulies , freebsd-questions@freefall.cdrom.com Subject: Re: using tcpdump effectively References: <199806151447.QAA29137@gilberto.physik.RWTH-Aachen.DE> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Mailer: Mutt 0.81e In-Reply-To: ; from Doug White on Mon, Jun 15, 1998 at 08:29:47PM -0700 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Mon, Jun 15, 1998 at 08:29:47PM -0700, Doug White wrote: > On Mon, 15 Jun 1998, Christoph Kukulies wrote: > > > > > To trace down why some network based X11 sessions are spuriously failing > > I' trying to use tcpdump. > > > > What sporadically happens is that a X session to our Mentor Design Architect > > running on HP is ceased and the connection breaks (we login via rlogin > > and start the X client with DISPLAY set to the FreeBSD machine.) > > > > When the connection breaks we see something like 'no route to host' > > Most likely the client is loosing the network connection to the host, > either by damage to the routing tables on the client or on an intermediate > network device. Run a traceroute to the HP box when MDA crashes and see if > it fails anywhere. As stated in a previous reply, it happens even on the local ethernet. So there is no hop involved and I don't see a reason why there should be a 'route lost' or no 'route to host'. > > > Could that be caused by denial of service attacks? What exactly is a denial > > of service attack? > > A denial of service attack (DoS) attempts to keep a machine from being > servicable by overwhelming it with requests or by disabling a server, > rending it useless. OK, this doesn't seem to be the case here. > > Doug White | University of Oregon > Internet: dwhite@resnet.uoregon.edu | Residence Networking Assistant > http://gladstone.uoregon.edu/~dwhite | Computer Science Major > NOTICE: Make sure your mailer replies to dwhite@resnet or I won't get it! -- --Chris Christoph P. U. Kukulies kuku@gil.physik.rwth-aachen.de To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message