From owner-freebsd-net  Fri Feb 26  8:18: 1 1999
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Date: Fri, 26 Feb 1999 10:17:24 -0600 (CST)
From: Mike Jenkins <mjenkins@carp.gbr.epa.gov>
Message-Id: <199902261617.KAA01232@carp.gbr.epa.gov>
To: david@compusyssolutions.com
Subject: Re: ARP is not my friend.
Cc: freebsd-net@freebsd.org
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> down in th the states.  I am on "the wave" - cable modem up in Canada.

Ah ha.  The cable side looks like an ethernet and people have machines
with private IP addresses that match your internal ones and it is
confusing FreeBSD.  You might try hardcoding your ARP table (at boot
time?) with the arp command (man 8 arp).

> In the O'reilly book TCP/IP Network Admin. book by Craig Hunt, there is some
> discussion about ARP_PROXYALL options in
> the basic BSD kernel config.  ...on page 114 "Proxy ARP is a variant on the

FreeBSD supports this if you have arpproxy_all="YES" in /etc/rc.conf at boot
time which /etc/rc.network uses to "sysctl -w net.link.ether.inet.proxyall=1".
I doubt that you have this on but you might check.  If it is on, turn it off
otherwise you'll cause problems for folks on the cable side.  They'll ARP
looking for 192.168.0.X and your host will answer.

> I am not sure I understand all that but this is the only reference I found

Proxy ARP helps hosts reach other hosts that they think are on the same
ethernet but are really behind a router.  I believe it was created because
some older hosts didn't understand subnet masks.  People split their single
ethernet into multiple ethernets separated by a router and using IP subnets.
The old hosts couldn't reach the other subnets because they thought everyone
was on one ethernet.  Thus Proxy ARP was born.

A good reference on Proxy ARP and more is "Introduction to Administration of
an Internet-based Local Network" by Charles L. Hedrick.  It can be found at
ftp://athos.rutgers.edu/runet/tcp-ip-admin.doc.

Mike


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