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Date:      Wed, 06 May 1998 22:37:36 -0600
From:      Clod Baldrick <baldrick@rmsq.com>
To:        Doug White <dwhite@resnet.uoregon.edu>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: Bizarre routing problem
Message-ID:  <35513A90.DFD1E29E@rmsq.com>
References:  <Pine.BSF.3.96.980506163658.6723C-100000@gdi.uoregon.edu>

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Doug White wrote:
> On Wed, 6 May 1998, Clod Baldrick wrote:
> > I can't take down the FreeBSD box to boot a new kernel at the moment (it's
> > in use), but I ran tcpdump on the Linux box.  (I'm taking out the packets
> > from corsair because that's where I'm logged in from.)
> >
> > lancaster# tcpdump -i eth0 host tomcat and not src corsair > tcp
> > tcpdump: listening on eth0
> >
> > tomcat$ ping lancaster
> > PING lancaster (130.13.21.91): 56 data bytes
> > ^C
> > --- lancaster ping statistics ---
> > 4 packets transmitted, 0 packets received, 100% packet loss
> >
> > And after ^C-ing the tcpdump on lancaster:
> > 0 packets received by filter
> > 0 packets dropped by kernel
> 
> Okay, that helps quite a bit -- we know that the packets aren't getting
> there.  Now the question is if they are being sent and if they are, where
> are they going??
> 
> I *really* need to see this from tomcat's point of view.  Try to find a
> quiet moment and sneak a reboot in.

"A quiet moment."  Well, it's now after 10pm, so...

tomcat# tcpdump -i ed2 ether host lancaster and not host corsair

> While you're at it check the routing tables and arp tables and make sure
> nothing silly's happened to the linux box's entries, ie now it points into
> space.  Also check that no one has swiped the linux box's ip address.

We may be onto something now.

lancaster# netstat -r
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt
Iface
130.13.21.0     *               255.255.255.0   U      1500 0          0
eth0
127.0.0.0       *               255.0.0.0       U      3584 0          0 lo

That doesn't look like the problem.

There was, however, a problem with the ARP tables.

lancaster# arp -v -a tomcat
Entries: 2      Skiped: 2       Found: 0
arp: in 2 entries no match found.

tomcat# arp lancaster
lancaster (130.13.21.91) at (incomplete)

So...

lancaster# arp -s tomcat 00:c0:0c:b0:5e:92
lancaster# arp -a tomcat
Address                 HWtype  HWaddress           Flags Mask           
Iface
tomcat                  ether   00:C0:0C:B0:5E:92   CM    *              
eth0

tomcat# arp -d lancaster
lancaster (130.13.21.91) deleted
tomcat# arp -s lancaster 00:A0:24:72:12:A7
tomcat# arp lancaster
lancaster (130.13.21.91) at 0:a0:24:72:12:a7 permanent

I made sure I copied the hw addresses exactly from the ifconfig on the
appropriate
machine.

So far so good.  But...

lancaster# traceroute tomcat
traceroute to tomcat (130.13.21.92), 30 hops max, 40 byte packets
 1  * *^C

tomcat# traceroute lancaster
traceroute to lancaster (130.13.21.91), 30 hops max, 40 byte packets
 1  * *^C

Grrr.

And:

tomcat# tcpdump -i ed2 ether host lancaster and not host corsair
tcpdump: unknown ether host 'lancaster'

lancaster is in /etc/hosts (with all the other hosts on the LAN) and nothing
else has its IP address -- that was one of the first things I checked.

Thanks for your continuing help.  I hope there's enough data here for you to
be able to work out what I'm doing wrong.

Regards.

-- 
Clod Baldrick
RMS, Longmont CO

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