Fwd: Re: ipchains

[Christian Fernandez]

----------  Mensaje Reenviado  ----------
Subject: Re: ipchains
Date: Mon, 17 Apr 2000 17:38:04 -0400
From: Christian Fernandez <rek2 at screamdesign.com>


Now that we are talking about ipchains....

I always used like a ip filtering firewall...
with masq.

now i need to put some servers inside with real ips, sure I use forwarding???
sure i put another nic card?


Thanks

El lun, 17 abr 2000, escribiste:
> 
> Today, Peter Farrar gleaned this insight:
> 
> >      I'm not sure.  I don't have any reference readily available.  But I 
> >      believe the -P in '/sbin/ipchains -P forward DENY' is for Purge.  So 
> >      everything preceding this line will be lost.  Try putting this line in 
> >      the front of your script.  Remember that your ipchains rules will be 
> >      executed in the order you declare them,
> 
> No, that's not correct.  The -P sets the default policy. The option you're
> thinking of is -F which flushes the ipchains tables.
> 
> You should actually set the -P rules FIRST. 
> 
> > After upgrading to my dual CPU and having various problems I decided to 
> > re-install RedHat 6.1.  Well this solved all the problems except one.  My 
> > ipchains no longer work.  The internal network appears fine (my Win95 box 
> > can ping the internal card on the Linux box and see the samba shares).
> > I ran a few basic check, the Linux machine can ping the windows one,
> > The win95 machine can ping the _internal_ network card on the Linux box. 
> > The win95 machine cannot ping the _external_ network card on the Linux box.
> 
> As far as ping goes, you need to make sure you've got ICMP forwarding
> built into your kernel.  You probably need to rebuild your kernel. Does
> anything else work?  Do you get errors from your script?
> 
> >      
> > eth0 is my external network card
> > 90.0.0.x is my internal network (that worked fine before the upgrade) 
> > The kernel is 2.2.12-20smp
> 
> You shouldn't use 90.0.0.x addresses.  I don't know if they are currenlty
> assigned, but that is a real network on the internet. If you want to use a
> class A address range, use 10.X.X.X instead.  BUT you probably will never
> need more than a class C, so I'd suggest using 192.168.somethingorother.
> 
> > Here is the script, I don't see anything wrong with it.  
> 
> I dunno, it looks o.k., but I'm not very awake at the moment either...
> 
> > --- begin include ---
> >      
> > /sbin/depmod -a 
> > /sbin/modprobe ip_masq_ftp 
> > /sbin/modprobe ip_masq_raudio 
> > /sbin/modprobe ip_masq_irc 
> > echo "1" > /proc/sys/net/ipv4/ip_forward 
> > echo "1" > /proc/sys/net/ipv4/ip_dynaddr 
> >      
> > /sbin/ipchains -M -S 7200 10 160 
> > /sbin/ipchains -A input -j ACCEPT -i eth0 -s 0/0 67 -d 0/0 68 -p udp 
> > /sbin/ipchains -P forward DENY 
> > /sbin/ipchains -A forward -s 90.0.0.0/24 -j MASQ 
> 
> 
> -- 
> PGP/GPG Public key at http://cerberus.ne.mediaone.net/~derek/pubkey.txt
> ------------------------------------------------------
> Derek D. Martin      |  Unix/Linux Geek
> derekm at mediaone.net  |  derek at cerberus.ne.mediaone.net
> ------------------------------------------------------
> 

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