I said I knew how to do proxy arp a while ago.  I take it back.

I have two Ethernet interfaces on my machine.  I want to use proxy arp to
suck packets off of the main interface so they get sent to the other one.
I know how to do that if it's a ppp interface, but for Ethernet I can't see
how to distinguish which interface does what arp.

My setup:
mc0 inet 137.78.218.53 netmask 255.255.255.0, default gateway 137.78.218.1
ae0 inet 137.78.218.137 netmask 255.255.255.248

printer on ae0, address 137.78.218.138, default gateway 137.78.218.137

arp -a shows a permanent entry for xx.53, a temporary entry for xx.138, but
none at all for xx.137.

lpr to printer works on the macbsd box;  the default routing entries seem
correct.  No IP traffic from outside gets forwarded though.

Another specific question:  is IPFORWARDING turned on by default in GENERIC
kernels?

Maybe I'm overthinking this.  If I put in the arp entry and they get
advertised on both interfaces the printer won't care because it doesn't do
arp for itself.  Will the MacBSD box stop being able to route the packet
because it already has an ethernet address translation for the IP number
though?

If I "can't get there from here"  can I make an Ethernet interface
point-to-point instead of broadcast?

Signature failed Preliminary Design Review.
Feasibility of a new signature is currently being evaluated.
h.b.hotz@jpl.nasa.gov, or hbhotz@oxy.edu