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Date:      Tue, 20 Jun 2000 12:31:18 -0400
From:      "Richard P. Kernin" <rpk@niagara.edu>
To:        "'freebsd-questions@FreeBSD.ORG'" <freebsd-questions@FreeBSD.ORG>
Cc:        "Richard P. Kernin" <rpk@niagara.edu>
Subject:   Network Interface Grabbing Random IP Addresses
Message-ID:  <0D274047A242D2119B1D006008C19DD67B85A6@POBOX>

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Hi,

We've been experiencing some strange behavior on one of
our FreeBSD boxes for the last few months.  Originally
the system was running v2.2.x with an Intel EtherExpress
NIC (fxp0), but when we started experiencing problems we
upgraded to the current revision of the time v3.4 and
upgraded the hardware moving to a 3Com XL NIC (xl0) to
be consistent with what we are using in other areas.
What is happening is that the system appears to be grabbing
random IP addresses, aliases, in addition to it's statically
assigned IP address, then dropping them after a time.  The
arp tables reflect the aliases, and quickly fill up, all
for the same MAC address.

? (xxx.xx.xxx.24) at 0:50:4:3:xx:xx permanent [ethernet]
? (xxx.xx.xxx.76) at 0:50:4:3:xx:xx permanent [ethernet]
? (xxx.xx.xxx.80) at 0:50:4:3:xx:xx permanent [ethernet]
? (xxx.xx.xxx.89) at 0:50:4:3:xx:xx permanent [ethernet]
? (xxx.xx.xxx.94) at 0:50:4:3:xx:xx permanent [ethernet]
[etc]

xl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
        inet xxx.xx.xxx.3 netmask 0xffffff00 broadcast xxx.xx.xxx.255
        inet xxx.xx.xxx.214 netmask 0xffffffff broadcast xxx.xx.xxx.214
        ether 00:50:04:03:xx:xx
        media: 100baseTX <full-duplex>
        supported media: autoselect 100baseTX <full-duplex> 100baseTX
<half-dupl
ex> 100baseTX 10baseT/UTP <full-duplex> 10baseT/UTP <half-duplex>
10baseT/UTP

The subnet that this machine is on has it's IP addresses assigned
via DHCP, except for a block set aside for static assignment
(of which this server is statically assigned).  We are using
ISC DHCP server running on FreeBSD, on another server v3.4 that
is functioning properly.  As a result of this machine grabbing
random IP addresses/aliases it eventually "bumps" into workstations
that are legitimately assigned the IP addresses (not a good thing).
I've upgraded the operating system, replaced the hardware, used
the generic kernel, as well as the compiled kernel we use specifically
for that system, all to no avail.  We've successfully used FreeBSD
(and the originally 386BSD! ;-) for 5+ years without problems, so
this is the first time we've been stumped.  The machine is running
the Apache webserver, but is not doing any virtual hosting, and we
don't do IP aliasing on any of our systems (am familar with how to
do this, as we did it years ago on now defunct systems for a project).

Any suggestions or insight into what might be causing this behavior
is greatly appreciated.

Thank you.

-rpk

----------
Richard P. Kernin
Assistant Director, Information Technology
Niagara University, NY 14109-2019
Internet: rpk@niagara.edu


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