Re: [gentoo-user] iptables configuration problem

["Chuanwen Wu" <wcw8410@gmail.com>]

Thank Norberto and Dan Farrell!I think i had a misunderstand and made
some mistakes.I hope I have correct it now.

/etc/conf.d/net in the server
config_eth0=( "202.114.10.134 netmask 255.255.255.0 brd 202.114.10.255" )
routes_eth0=( "default gw 202.114.10.129" )

config_eth1=( "192.168.1.1 netmask 255.255.255.0 brd 192.168.1.255" )

/etc/conf.d/net in a PC
config_eth0=( "192.168.1.35 netmask 255.255.255.0 brd 192.168.1.255" )
routes_eth0=( "default gw 192.168.1.1" )

2007/5/15, Dan Farrell <dan@spore.ath.cx>:
> Greetings all.  Hope the weather in bejing is pleasant, Mr Wu.
>
> On Mon, 14 May 2007 11:58:34 -0300 (ART)
> "Norberto Bensa" <nbensa@gmx.net> wrote:
>
> > On Mon, May 14, 2007 8:23 am, Chuanwen Wu wrote:
> > > Thank you!I think i have done what you meant.
> > > Here is the information:
> > >
> > >
> > > /etc/conf.d/net in the server
> > > config_eth0=( "202.114.10.134 netmask 255.255.255.0 brd
> > > 202.114.10.255" ) routes_eth0=( "default gw 202.114.10.129" )
> >
> > OK
>
> > >
> > > config_eth1=( "192.168.1.63 netmask 255.255.255.0 brd
> > > 192.168.1.255" ) routes_eth1=( "default gw 192.168.1.1" )
> >
> > You don't need a route here.
> More exactly, a route to the subnet 192.168.1.0/24 will automatically
> be created through eth1.  A _gateway_ in this case is not necessary
> because eth1 lives on that subnet.
> >
> > > /etc/conf.d/net in one PC
> > > config_eth0=( "192.168.1.35 netmask 255.255.255.0 brd
> > > 192.168.1.255" ) routes_eth0=( "default gw 192.168.1.1" )
> >
> > No. GW should be 192.168.1.63, which is the IP address of your
> > gateway.
> > HTH,
> > Norberto
> >
> First, the firewall configuration.  Your first message said:
> > The eth0 here has the real ip,and the eth1 have a subnet
> > ip:192.168.1.21.
> But here you show that you set it to .63, as Norberto pointed out.  I
> assume that was just a typographical error in the first email. Moving
> on, the default route for the firewall is probably to the outside
> world, and if you can ping google.com, it works.
>
> Second, the client configuration.  The route for the subnet it's on
> (192.168.1/24) is automatically created, as before.  The default route
> is the IP of the firewall/gateway it's behind, namely 192.168.1.63 as
> Norberto said.  The machine that's forwarding packets to the internet
> for these hosts now provides the route to the outside world for these
> hosts.
>
> Third, you must tell your client PCs nameservers, so that they can
> resolve domain names.  If you fail to do so, even though a ping of
> google.com, for example, fails, a ping of its ip address
> (64.233.167.99, in my case) will work.

All my PCs have the same /etc/resove.conf file with the server.And now
the PC can't ping through 66.249.89.99(of course,the server can).

>
> Fourth, you must check your firewall (that is, iptables) configuration
> to be sure your iptables all refer to the correct subnet.
> > iptables --table nat -A POSTROUTING -s 192.168.8.0/24 -j MASQUERADE
> that wasn't right -- obviously the subnet should be your own.

I have already corrected it to "iptables --table nat -A POSTROUTING -s
192.168.1.0/24 -j MASQUERADE" from the first time.

>
> Since the firewall you're building knows all the information the hosts
> need to know (subnet information, routes, etc) you may wish to set up a
> rudimentary DHCP server on it, so that additional hosts can be added
> without configuration by the user.  You may also wish to  impliment a
> caching, recursive nameserver for enhanced efficiency.  DNSMasq can do
> both.
Thanks for your advice!
> --
> gentoo-user@gentoo.org mailing list
>
>
When a PC ping 66.249.89.99,I got these information from the server:

# tcpdump -n -i eth1 net 192.168.1.0/24 and port not 22 and not arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1, link-type EN10MB (Ethernet), capture size 96 bytes
10:01:08.214160 IP 192.168.1.35 > 66.249.89.99: ICMP echo request, id
35391, seq 599, length 64
10:01:09.214014 IP 192.168.1.35 > 66.249.89.99: ICMP echo request, id
35391, seq 600, length 64
10:01:10.213899 IP 192.168.1.35 > 66.249.89.99: ICMP echo request, id
35391, seq 601, length 64
10:01:11.213792 IP 192.168.1.35 > 66.249.89.99: ICMP echo request, id
35391, seq 602, length 64
10:01:12.213676 IP 192.168.1.35 > 66.249.89.99: ICMP echo request, id
35391, seq 603, length 64

5 packets captured
5 packets received by filter
0 packets dropped by kernel


And

# tcpdump -n -i eth0 net 202.114.10.134 and port not 22
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes


Does it mean that eth1(the interface in my subnet) receive the request
but don't post forward it?
-- 
wcw
-- 
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