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Date:      Tue, 18 Sep 2001 22:00:42 -0500 (CDT)
From:      Mike Saunders <method@method.cx>
To:        freebsd-net@freebsd.org
Subject:   SOLVED - kernel arp messages 
Message-ID:  <Pine.NEB.4.21.0109182150210.7793-100000@schizo.method.cx>
In-Reply-To: <Pine.BSF.4.21.0109181856480.23317-100000@InterJet.elischer.org>

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On Tue, 18 Sep 2001, Julian Elischer wrote:

> Date: Tue, 18 Sep 2001 19:05:21 -0700 (PDT)
> From: Julian Elischer <julian@elischer.org>
> To: Mike Saunders <method@method.cx>
> Cc: Lars Eggert <larse@ISI.EDU>, freebsd-net@freebsd.org
> Subject: RE: kernel arp messages
> 
> 
> > > Date: Tue, 18 Sep 2001 17:31:24 -0800
> > > From: Lars Eggert <larse@ISI.EDU>
> > > To: Mike Saunders <method@method.cx>, freebsd-net@freebsd.org
> > > Subject: RE: kernel arp messages
> > > 
> > > > Sep 18 15:01:54 router /kernel: arp: 209.74.87.1 is on lo0 but got reply
> > > > from 00:60:08:35:57:4e on xl0
> > > 
> > > And this is *really* ugly! Are you proxy-arping? Someone is advertising
> > > one of your local IP addresses.
> > 
> 
> how did that address get on lo0?
> what is netstat -r (or ifconfig) showing?

That is a good question.  I don't really know how, that's just what the
kernel tells me.

> 
> > Actually Lars,
> > 	If you notice the MAC, it's the same as:
> >  
> > ep0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> >         inet 209.74.87.1 netmask 0xffffff00 broadcast 209.74.87.255
> >         ether 00:60:08:35:57:4e
> > 
> > So 209.74.87.1 is on ep0 which is on lo0 but gets caught at xl0, according
> > to this machine.
> 
> 
> ep0 is NOT "ON" lo0
> What makes you say  that strange thing?
> 
> 

What I meant was "This is what the machine is thinking."  I know that ep0
is not "on" lo0.



> 
> 
> > 
> > So maybe a picture will help
> > 
> > 			|
> > 			|
> > 			|
> > 		   209.74.92/24
> > 			|
> > 		      (xl0)
> > 		  FreeBSD Router
> > 		      (ep0)
> > 			|
> > 		   209.74.87/24
> > 			|
> > 		     switches
> > 
> > This is what I believe to be the current set up.  Now that I read the
> > email mentioning the loop, it's possible that somebody has thrown in a hub
> > connecting both networks.  I know there's one in the closet.  I'll have to
> > go and check.
> 
> that would be my guess.
> 
> > 
> > 	Ideally, all I'm trying to do is route one class C into my
> 
> what is  the link to the provider?
> 


In return for a free T1 we do some co-location for our provider.  There's
an 8-port hub that sits between my external interface and the
router.  There's a few other machines and a bay networks access node
plugged into this hub.  turns out somebody plugged a patch cable from this
hub (sitting on the provider's network) into our stack of switches.  I
believe it was Chris that nailed this one on the head.  

Thanks for the tips everybody.  I've been looking at that for a long time,
I don't know how I missed that cable, or how it got there.  So in reality,
the network setup looked like this.

		  provider
		   router
		     |-----------\	
 		    Hub		 |
		     |		 |
                209.74.92/24	 |
                     |		 |
                   (xl0)	 |	
               FreeBSD Router	 |
                   (ep0)	 |
                     |		 |
                209.74.87/24	 |
                     |		 /
                  switches------/
                      

	Once again, thanks for the quick replies and the help.  It's much
appreciated.

-Mike Saunders
method@method.cx





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