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Date:      Mon, 22 Feb 1999 11:38:57 -0600
From:      Anthony Kim <akim@itisolutions.com>
To:        freebsd-questions@freebsd.org
Subject:   IPFW & NAT question
Message-ID:  <3.0.6.32.19990222113857.009ad5d0@forbes.itisolutions.com>

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I'm trying to come up with a solution as follows please let me know if this
is workable:

Given a 2.2.8-STABLE box running IPFW & NAT

The firewall will have 3 NICS.
NIC1 - Real IP; to Internet
NIC2 - Real IP; to Perimeter network <--> on this network another HOST
(HOST A) with Real IP
NIC3 - Private IP; to Internal network

NIC1 & NIC2 & HOST A will all be on the same network address.


I've done ipfw several times with 2 network cards. How is FreeBSD going to
handle this 3rd card? NIC1 & NIC2 will be on the same network ID. On the
perimeter network will be a bastion host having a real IP on the same
network. I was thinking maybe I could bridge between NIC1 & NIC2. Or will
static routing work in this case? I'm unsure.

I'm aware of the -u flag to natd to enable translation only for rfc1918
compliant addresses. Real IPs will be passed untranslated. Will routing be
a problem? I'm thinking, if on the firewall I added the following example
this might work(?):

route add default <defaultrouter>
route add -host <Host with Real IP> <NIC2 IP>
route add -net <Internal Network> <NIC3 IP>

...

The alternative solution is to enable translation on HOST A with another
fake IP network but using static NAT. IOW:

EXT NETWORK: real
PERIMETER NETWORK: 192.168.16.0
INTERNAL NETWORK:  192.168.17.0
where HOST A on the perimeter network will be static NAT to its real IP.
If I were to do this, where do I assign HOST A's real IP? As an alias to
the firewall's external NIC? How can FreeBSD handle NAT using more than one
public IP?

I appreciate any direction. Thanks!


Anthony Kim
Sysadmin, HFR Group
http://www.hfr.com/



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