Correct way to configure an IP range for firewall

Al Plant noc at
Wed Sep 9 19:14:48 UTC 2009

Maxim Khitrov wrote:
> Hello all,
> A quick question - I have a /29 block of IPs that needs to be handled
> by a firewall I'm setting up. Two addresses are lost to broadcast and
> network, one is the ISP gateway, so we end up with 5 usable IPs that
> can be assigned to the external interface. The question is how to do
> this correctly?
> I want only one of the addresses assigned to the firewall itself,
> another will be used as the public nat address for all hosts on the
> lan. Remaining three addresses will be used as bidirectional nat for
> servers.
> Am I correct in assuming that I just need to add four
> ifconfig_vr0_alias[0-3] lines to rc.conf? What happens if in the
> future we get a much bigger IP block, is there a more efficient way of
> accomplishing the same thing? I don't actually want the firewall to
> consider itself the final destination for any of the additional IPs,
> it just needs to pass them to pf for nat and filtering.
> - Max
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Aloha Max,

What you have sounds like an ATM ( Asynchronous Transfer Mode ) circuit. 
I have one here that is for three servers a desktop and one spare IP.

I got the setup from Michael Paoli at in California.

With setup I had to put firewalls (PF) on the three servers facing the 
internet and the desktop as well. There are 2 references I used for this 
firewall setup. Absolute FerrBSD - M. Lucas Pg. 273 and Peter 
Hansteen. Both are on this list.

If you would like to see the three sheets on how I set this up I can fax 
them to you or email.

The setup for more IP's should be scalable but the IP's and default 
route would change I would think. You could keep using /29 ATM blocks 
and increase in increments with different IP's most likely with out 
changing the first ones.

~Al Plant - Honolulu, Hawaii -  Phone:  808-284-2740
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