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I'm setting up a NAT for a connected router to my laptop using the following command (IP forwarding is enabled):

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

So basically I have a eth0 which is my laptop's LAN, and a USB-CAT5 -based connection from my laptop to a wireless router, which is eth1. And I am assigning a static IP to my eth1 interface (i.e. connected to the wireless router) using the following command:

sudo ifconfig eth1 netmask up

And I run ifconfig to make sure eth1 has this IP address:

eth0  Link encap:Ethernet  HWaddr 28:d2:44:77:39:0e  
      inet addr:  Bcast:  Mask:
      inet6 addr: 2002:c023:9c17:118:f5ea:ed5a:6c19:138d/64 Scope:Global
      inet6 addr: fe80::2ad2:44ff:fe77:390e/64 Scope:Link
      inet6 addr: 2002:c023:9c17:118:2ad2:44ff:fe77:390e/64 Scope:Global
      RX packets:289511 errors:0 dropped:324 overruns:0 frame:0
      TX packets:103659 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:87784569 (87.7 MB)  TX bytes:26739445 (26.7 MB)
      Interrupt:20 Memory:f0600000-f0620000 

eth1  Link encap:Ethernet  HWaddr 00:50:b6:0a:4c:5e  
      inet addr:  Bcast:  Mask:
      UP BROADCAST MULTICAST  MTU:1500  Metric:1
      RX packets:2268 errors:0 dropped:0 overruns:0 frame:0
      TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
      collisions:0 txqueuelen:1000 
      RX bytes:104328 (104.3 KB)  TX bytes:0 (0.0 B)

The router's settings has been setup. My problem is that when I'm connected to the router, I don't have any internet connection. Can someone help me with that?

share|improve this question

You also need to tell the machine that's acting as a router to forward the packages it receives and configure the default gateway, use this command:

sudo sysctl net/ipv4/ip_forward=1

To add a default gateway, also add:

sudo route add -net default gw X.X.X.X

Where X.X.X.X is the IP of your wireless router.

share|improve this answer
is it different than echo 1 > /proc/sys/net/ipv4/ip_forward , which enables IP_forwarding?! – Tina J May 30 '14 at 21:52
It's the same order, but using sysctl. The result is the same, yes. – darent May 30 '14 at 21:54
So, yeah...As I said, it is already enabled. – Tina J May 30 '14 at 21:55
Try also enabling the gateway, see if that's the problem. – darent May 30 '14 at 21:57
So xxx should be the static IP I've been trying to assign, right? – Tina J May 30 '14 at 21:58

Test this:

sudo su

iptables -F

iptables -A INPUT -i lo -j ACCEPT

iptables -A INPUT -s -i eth1 -j ACCEPT

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

echo 1 > /proc/sys/net/ipv4/ip_forward  
share|improve this answer
Well; no changes. One thing which I'm not sure about is that when I click on the network icon near the clock, for eth1's wired network, it shows disconnected! However ifconfig shows it as UP ! – Tina J May 30 '14 at 22:16

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