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Date:      Mon, 28 Aug 2000 18:01:04 -0400 (EDT)
From:      Bruce Petro <bpetro@usa.com>
To:        freebsd-questions <freebsd-questions@FreeBSD.ORG>
Subject:   RE: ipfw setup when dhcp?
Message-ID:  <384197957.967500064518.JavaMail.root@web302-mc.mail.com>

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Michael, thanks for the reply - yes, you have a good point, after I reviewed the contents of the rc.firewall that they had documented on http://www.mostgraveconcern.com/freebsd/ (The dual-homed host article - which is what I was going by), I see that the only use of the actual onet and omask and inet and imask was to perform the rules he titles: # Stop spoofing. (see details below). 

So, can anyone share is the #stop spoofing possible to do when you are under dhcp and not able to know ahead of time what your onet and omask are going to be?  I know inet and imask are static, and well, I guess you could assume the omask is pretty static, but still the onet address remains quite dynamic...

Any ideas?
Thanks,
Bruce.
************************************************************
PS: HERE IS THE TEXT FROM mostgraveconcern.com TO SHOW WHAT THEY ARE DOING TO ACCOMPLISH THE SPOOFING PROTECTION ...
# Outside interface network and netmask and ip
oif="dc0"
onet="123.45.67.0"
omask="255.255.252.0"
oip="123.45.67.89"

# Inside interface network and netmask and ip
iif="ep0"
inet="10.0.0.0"
imask="255.255.255.0"
iip="10.0.0.1"

# Stop spoofing
${fwcmd} add deny log all from ${inet}:${imask} to any in via ${oif}
${fwcmd} add deny log all from ${onet}:${omask} to any in via ${iif}
*************************************************************
Michael wrote:

>
>Bruce, I use roadrunner myself, and I have not had to enter this info in
>rc.firewall.  Have a look at
>http://www.defcon1.org//html/Networking_Articles/Firewall-Ipfw/firewall-ipfw
>.html
>
>This is the guide I used to setup my firewall.  Setup up two of them, and
>they work like champs.
>
>...Michael...
>
>> -----Original Message-----
>> From: owner-freebsd-questions@FreeBSD.ORG
>> [mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Bruce Petro
>> Sent: Monday, August 28, 2000 11:59 AM
>> To: freebsd-questions
>> Subject: ipfw setup when dhcp?
>> 
>> 
>> Can someone advise what to do in this - I know in setting up 
>> ipfw, part of what you should do is setup the following in 
>> rc.firewall...
>> 
>> # Outside interface network and netmask and ip
>>              oif="dc0"
>>              onet="123.45.67.0"
>>              omask="255.255.252.0"
>>              oip="123.45.67.89"
>> 
>> But when you are connecting to dhcp (roadrunner) what are you 
>> supposed to put into these?  Should you put your 'currently 
>> assigned' address with the current mask and that in effect 
>> would define you possible addresses?  Or is there some 
>> notation that will simply echo whatever address I've been 
>> given this time?
>> 
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