Re: Notebook as Internet client as well as router (for the other computers)

[David <david_moerike@arcor.de>]

At present time I don't understand all commands in the script;

however, using "sniffit", I found out something:

On the second computer (client), if a ping package is sent for the 
internet, that is, for an address that does not begin with 169.254 (they 
come from avahi) the source address is not 169.254.10.246, but 0.0.0.0 - 
Why?

Is that a bug? If yes, is there a workaround for it?

The command on the client: route add default gw 196.254.195.183

- that is the local address of the notebook - has no effect on this. Why?

However, the command:

iptables -t nat -o eth0 -A POSTROUTING -j MASQUERADE

shouldn't it replace the 0.0.0.0 with the address that I got (through 
dhclient during system startup) from the provider, just as it replaces 
the local address with the address from the provider? Why doesn't it do 
that?

Jordi Ferrando Fabra schrieb:
> Hi David,
> Attached my firewall script, hope it helps.
> Good luck.
>
> David wrote:
>   
> > Hello,
> >
> > I have a MBO "eurobook" 8375 - equiv. to Mitac 8375, running Squeeze - 
> > the Internet connection through the Cable modem to "KabelBW" works fine.
> >
> > However, I also want to connect the other computers through it (in the 
> > notebook is eth0 the built-in card and is connected to the Internet, 
> > eth2 to the LAN).
> >
> > Please help me to find out if I forgot sth (for example a kernel 
> > module), or if I made sth. wrong, or if it isn't successful because of 
> > a bug.
> >
> > eurobook-debian:/home/david# echo 1 > /proc/sys/net/ipv4/ip_forward
> > eurobook-debian:/home/david# cat /proc/sys/net/ipv4/ip_forward
> > 1
> >
> > eurobook-debian:/home/david# modprobe -v iptable_nat
> > insmod /lib/modules/2.6.26-2-686/kernel/net/netfilter/nf_conntrack.ko
> > insmod 
> > /lib/modules/2.6.26-2-686/kernel/net/ipv4/netfilter/nf_conntrack_ipv4.ko
> > insmod /lib/modules/2.6.26-2-686/kernel/net/netfilter/x_tables.ko
> > insmod /lib/modules/2.6.26-2-686/kernel/net/ipv4/netfilter/nf_nat.ko
> > insmod /lib/modules/2.6.26-2-686/kernel/net/ipv4/netfilter/ip_tables.ko
> > insmod /lib/modules/2.6.26-2-686/kernel/net/ipv4/netfilter/iptable_nat.ko
> > eurobook-debian:/home/david# iptables -A POSTROUTING -t nat -j MASQUERADE
> >
> > eurobook-debian:/home/david# iptables -t nat --list-rules
> > -P PREROUTING ACCEPT
> > -P POSTROUTING ACCEPT
> > -P OUTPUT ACCEPT
> > -A POSTROUTING -j MASQUERADE
> >
> > eurobook-debian:/home/david# iptables -t nat --list
> > Chain PREROUTING (policy ACCEPT)
> > target     prot opt source               destination       
> > Chain POSTROUTING (policy ACCEPT)
> > target     prot opt source               destination        
> > MASQUERADE  all  --  anywhere             anywhere          
> > Chain OUTPUT (policy ACCEPT)
> > target     prot opt source               destination       
> > A ping to the other computers is successful. - On the other computer 
> > (there is also Squeeze running):
> >
> > #route add default gw 169.254.195.183
> >
> > To enter, for example, http://de.wikipedia.org in the browser, or a 
> > ping is not successful, even not a ping to 91.198.174.2 (that is the 
> > address at present time).
> >
> > Again checking the modules on the notebook:
> >
> > eurobook-debian:/home/david# lsmod |grep ip
> > iptable_filter          2624  0
> > ipt_MASQUERADE          2592  1
> > iptable_nat             4680  1
> > ip_tables              10160  2 iptable_filter,iptable_nat
> > nf_nat                 15544  2 ipt_MASQUERADE,iptable_nat
> > x_tables               13284  3 ipt_MASQUERADE,iptable_nat,ip_tables
> > nf_conntrack_ipv4      12268  3 iptable_nat,nf_nat
> > nf_conntrack           55540  4 
> > ipt_MASQUERADE,iptable_nat,nf_nat,nf_conntrack_ipv4
> > ipv6                  235364  29
> > crypto_blkcipher       15236  1 ecb
> >
> >
> >     
>
>