Neil A. Hillard said the following on 04/27/2006 06:10 PM:

>>>You can't have multiple interfaces with the same IP address.
>>
>>That's too bad; it's been a useful trick in several networks I've been
>>involved with.
> 
> I've never had cause to use that.  I can't think of why I'd need it
> instead of a bridged interface (unless you wanted multiple interfaces
> bridged.

It comes down to having a featureful bridge that can do filtering.  If
you don't have that, and you have a limited number of publically visible
IPs (for example, my block of five), using one address on both the WAN
and DMZ interfaces leaves one more to use for a machine on the DMZ.
> There isn't a downside!  Just go into the 'Advanced' menu and check
> 'Enable filtering bridge'.  Then add the necessary rules.  I wouldn't
> dream of giving the world access to my SIP server :-)

OK, even better.

Just to explain where I was coming from, to implement this with Linux
Router Project, I had NAT between LAN and WAN, plain old routing between
WAN and DMZ, and proxy ARP to advertise the DMZ machines out to the
Roadrunner-provided cable router that sat in front of the LRP machine.
If I can accomplish the same thing more simply, so much the better.

Thanks for the clarifications!

John