Natd stops working on Firewall

[Scot]

Thanks Ruslan ;
I'll give it a try right now.

Just want to send this out before I switch firewalls,
assuming I might be down for an hour or so tweaking.

oip and iip are static variables in rc.firewall but
under DHCP oip is a moving target. Is there a recommended
way to pass these to rc.firewall so a re-edit is not needed?

Thanks Again
Scot

-----Original Message-----
From: Ruslan Ermilov [mailto:ru at FreeBSD.ORG]
Sent: Tuesday, March 25, 2003 4:20 AM
To: Scot
Cc: FreeBSD Stable; ipfw at FreeBSD.ORG
Subject: Re: Natd stops working on Firewall


On Mon, Mar 24, 2003 at 09:52:32PM -0500, Scot wrote:
> Hi;
>
> Just setup my FreeBSD 4.7 Firewall using the docs
> outlined in the handbook.
>
What docs you have used to set up the firewall?

> The install went on and
> everything seems to be working fine then boom.
> The system seems to stop routing traffic. No
> messages in the security log or natd log as to why.
>
> I made sure it was logging by nmaping my box from the
> outside. I even ran natd in the foreground and it still didn't
> tell me what was going on.
>
> There is nothing in any logfile that tells me why this thing
> just stops working so I'm thinking it may not be a daemon but
> something in the kernel.
>
> I cannot ping the interface from the internal network but tcpdump shows
> the packets being received. (Hub network firewall_type=SIMPLE ).
>
> If I logon to the console the cable modem connection is still functioning
> and I can surf from the firewall.
>
> Any ideas on where to look next ??
>
>
> Cable modem using dhcp -> 192.168 home network on
> PPro w/280 MB ram.
> Intel Pro 10/100b/100+ Ethernet This card is a PCI card with 2 interfaces.
> Standard Xuser install + Kernel sources.
>
I've been through this just recently.  Our "simple" prototype
is not production ready; if you just tune oip/iip/onet/inet,
etc., it won't allow your internal machines to talk outside.

The packet flow for a machine in ${inet}:${imask} talking outside
is as follows:

${inet}:${imask} -> some_host (in  via ${iif})
${oip}           -> some_host (out via ${oif}) (after NAT)
some_host -> ${inet}:${imask} (in  via ${oif}) (after de-NAT)
some_host -> ${inet}:${imask} (out via ${iif})

(This assumes that you NAT using ${oip}, which is not always
the case.)

So, to make it work (if default is to "deny"), you need to add
the following rules at the end of the ruleset:

${fwcmd} add pass all from ${inet}:${imask} to any in via ${iif}
${fwcmd} add pass ip from ${oip} to any out via ${oif}
${fwcmd} add pass ip from any to ${inet}:${imask}


Cheers,
--
Ruslan Ermilov		Sysadmin and DBA,
ru at sunbay.com		Sunbay Software AG,
ru at FreeBSD.org		FreeBSD committer,
+380.652.512.251	Simferopol, Ukraine

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