multiple interfaces on same subnet?

Atom Powers atom.powers at
Wed Aug 2 03:03:01 UTC 2006

On 8/1/06, Malcolm Kay <malcolm.kay at> wrote:
> I have no personal experience of doing this, but it seems to me
> you should be able to achieve your objective by using a specific
> netmask with ifconfig rather than the CIDR / notation:
> -> netmask
> -> netmask

Creative idea ... even if it's breaking the rules ( so don't do it ).
Even if FreeBSD honors these subnets there is no guarantee that any
other hosts on the network will. Many systems will refuse to even
configure this kind of invalid subnet.

Plus, you can't easily scale this to the 10 networks the original
poster mentioned and it would be a nightmare to try and figure out how
to re-route traffic if one of the next-hop hosts died. (Which was also
a goal mentioned in the original post.)

Although I've head that IPFW can handle multiple dynamic redirects ( I
forswore all other firewalls as soon as I found pf ) you can do it
very simply with pf.

Perfection is just a word I use occasionally with mustard.
--Atom Powers--

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