Arp, Arp, Arp, Arppity Arp!

Aaron D. Gifford agifford at
Thu Feb 12 17:39:48 PST 2004

Imagine this:

[  To the Internet  ]
           | (ethernet MAC 00:11:22:aa:bb:cc, interface dc0)
[ My FreeBSD Router ]   (ethernet interface dc1)
           | ( is an alias address on this interface)
[  An Inside Host   ]

On the FreeBSD router has a static route for, telling it 
to forward traffic to that address to  Now all I need is 
for the FreeBSD to proxy ARP on the network on behalf of so it can forward traffic for the inside host.

So this is what I try, having never done static ARP stuff before on FreeBSD:

   arp -s 00:11:22:aa:bb:cc pub

(Side question: What's the difference between this command and the same 
command adding the keyword 'only' at the end?  The man page isn't very 
clear to me on what the difference is between "published" and "published 
(proxy only)" as far as what FreeBSD does in response to ARP requests 
for the address/host.)

Here's what I see when I try running the above command:

   set: proxy entry exists for non 802 device

Huh?  What?

What's the deal?  If this were a Cisco, this would be easy:

   cisco(config)# arp 0011.22aa.bbcc arpa eth0

So what's up with FreeBSD?  What magic incantation do I need to know?

Thanks in advance for any/all help/suggestions.

Aaron out.

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