Re: configure firewall & NAT & cache with each other (nfcan: addressed to exclusive sender for this address)

[Jim Laurino <nfcan.x.jimlaur@dfgh.net>]

On 2005.01.29 23:15, Alireza Yazdani - yazdani1193@yahoo.com wrote:
> 
> Hello all,
> 
> I have 2 box for cache, bandwidth manager, firewall, NAT .
> 
> one box is cache server(squid) only. and another box is bandwidth manager,
> firewall, NAT server.
> 
> I haven't any rule on my squid box. the default gateway of my users is my
> firewall box. my firewall box has 2 ethernet(user side and internet side).
> 
> ip of firewall box is :
> 
> iptables_box_ILAN=172.16.5.5 (user side)(eth0)
> 
> iptables_box_WLAN=212.213.38.100 (internet side)(eth1)
> 
> ip of cache box is :
> 
> squid_box=172.16.5.6
> 
> the default gateway of cache box is firewall box
> 
> I use of this rule for NAT :
> 
> iptables -t nat -A POSTROUTING -s 172.16.5.0/24 -o eth1 -j SNAT --to
> 212.213.38.100
> 
> now I want redirect the request on port 80 to cache box :
> 
> local_network=172.16.5.0/24
> 
> iptables_box_ILAN=172.16.5.5
> 
> iptables_box_WLAN=212.213.38.100
> 
> iptables -t nat -A PREROUTING -i eth0 -s ! $squid_box -p tcp --dport 80 -j
> DNAT --to $squid_box:3128
>

On reflection, the NAT source and destination syntax
is not quite right (you do not use --to) instead:

iptables -t nat -A PREROUTING -i eth0 -s ! $squid_box -p tcp --dport 80 -j
DNAT --to-destination $squid_box:3128


> iptables -t nat -A POSTROUTING -s $local_network -d $squid_box -o eth0 -j
> SNAT --to $iptables_box_ILAN
>

iptables -t nat -A POSTROUTING -s $local_network -d $squid_box -o eth0 -j
SNAT --to-source $iptables_box_ILAN

A SNAT rule like this allows clients on the local net to address a server
on the local net by the external ip address. The packets appear to come
from the firewall, therefore the server replies there. I do not see why
this is needed for a proxy. I think the proxy does need SNAT for itself
to reach the internet. Something like this, which you may already have:

iptables -t nat -A POSTROUTING -s $squid_box -o eth1
-j SNAT --to-source $iptables_box_WLAN


> iptables -A FORWARD -s $local_network -d $squid_box -i eth0 -o eth0 -p tcp
> --dport 3128 -j ACCEPT
> 
> when I don't use of NAT it is correct. and when I set all on one ethernet it
> is correct.
> 
> but when I have two ethernet and I NAT on firewall box it's not work  
> correct.
>

-- 
Jim Laurino
nfcan.x.jimlaur@dfgh.net
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