> Yes, that does work using proxyarp as long as the addresses are on
> the same subnet.  But what if they're not?

The only way I can see this as making any sense at all is if you want
your machine to proxy-arp for addresses on a subnet it does not itself
exist in (this usually means running more than one subnet on a given
broadcast domain).  Other than that, it doesn't make sense to proxy-arp
for an address that's not on-subnet, because if you aren't *on* a
subnet something is very very broken if you're seeing arps for that
subnet.

> Can NetBSD still do it?

Yes, but it needs a little *ahem* "persuading".

I've done this; at home I have a somewhat ugly hack that depends on
exactly the above situation.  I had to hack on arp(8) so as to be able
to specify the interface, instead of depending on software being able
to guess ("intuit") it.

ftp.rodents.montreal.qc.ca:/mouse/source-tree/patches/working/src/usr.sbin/arp/
contains the changes I made to arp.  They are for a fairly old version
of arp, but they may be useful as a guide if naught else.

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