Internet Connection Sharing Documentation

[tCarls]

I seem to be having a similar problem to kazbear. I followed the wiki and can ssh between the two computers but can't connect to the internet from the second one. kazbear, can you post what you did to fix it?

My laptop is connected to a wireless network. I'm trying to share the connection with my desktop through ethernet. I've tried using both static IPs and dhcp, with similar results. ssh works but the internet doesn't. The only difference is that with static IPs, when I ping google from the desktop it says it couldn't resolve the name and when I ping google's IP it says it's unreachable. However, with dhcp the pings don't print errors, they just timeout. Any ideas?

thanks

[dmizer]

Are you sure you configured the dns servers on the desktop, as described under "Client set up"?

[tCarls]

Are you sure you configured the dns servers on the desktop, as described under "Client set up"?

Fairly sure, unless I missed something. See below.

Actually, one thing important that I just now noticed: the ping on the desktop is actually able to resolve google's IP, it just can't transfer any data.

tcarls@desktop$ grep prepend /etc/dhcp3/dhclient.conf
#prepend domain-name-servers 127.0.0.1;
prepend domain-name-servers 208.67.222.222,208.67.220.200;

tcarls@desktop$ cat /etc/resolv.conf
search example.org
nameserver 208.67.222.222
nameserver 208.67.220.220
nameserver 208.67.216.132
nameserver 208.67.216.132

Below is the output of a few more commands that may be useful. Note: I changed the subnet from 192.168.0 to 192.168.2 so it wouldn't conflict with the wireless subnet.

tcarls@desktop$ route
Kernel IP routing table
Destination    Gateway    Genmask          Flags Metric Ref    Use Iface
192.168.2.0    *          255.255.255.0    U     0      0        0 eth0
default        laptop     0.0.0.0          UG    0      0        0 eth0


tcarls@desktop$ ifconfig eth0 | grep 'inet addr'
    inet addr:192.168.2.20 Bcast:192.168.2.20  Bcast:192.168.2.255  Mask:255.255.255.0

tcarls@desktop$ ping 192.168.2.1
PING 192.168.2.1 (192.168.2.1) 56(84) bytes of data.
64 bytes from 192.168.2.1: icmp_seq=1 ttl=64 time=0.000 ms
^C

--- 192.168.2.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.000/0.000/0.000/0.000 ms

tcarls@desktop$ ping www.google.com
PING www.l.google.com (209.85.173.147) 56(84) bytes of data.
^C

--- www.l.google.com ping statistics ---
60 packets transmitted, 0 received, 100% packet loss, time 59007ms

tcarls@laptop$ ifconfig eth0 | grep 'inet addr'
          inet addr:192.168.2.1  Bcast:192.168.2.255  Mask:255.255.255.0

tcarls@laptop$ ifconfig wlan0 | grep 'inet addr'
          inet addr:192.168.0.104  Bcast:192.168.0.255  Mask:255.255.255.0

tcarls@laptop$ cat /proc/sys/net/ipv4/ip_forward
1

# I'm using Hardy. The wiki said there's a bug in Gutsy and
# a couple lines need to be added. I wasn't sure if it still
# applied to Hardy to I tried with and without them.
tcarls@laptop$ grep forward /etc/sysctl.conf
# Uncomment the next line to enable packet forwarding for IPv4
net.ipv4.ip_forward=1
# Uncomment the next line to enable packet forwarding for IPv6
net.ipv6.ip_forward=1
#net.ipv4.conf.default.forwarding=1
#net.ipv4.conf.all.forwarding=1

[dmizer]

Okay, I've tested this on a few systems so it may also work for you.

Let's try dumping your current firewall configuration with the following command:

sudo iptables -F

Make sure there are no remaining iptables rules in place:

$ sudo iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Then try this firewall argument:

sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE

[Dmole]

>Open /etc/resolve.conf with your favorite text editor:
>sudo nano /etc/dhcp3/dhclient.conf

seems to me there is an error here because /etc/dhcp3/dhclient.conf != /etc/resolve.conf


also it did not work for me

[dmizer]

>Open /etc/resolve.conf with your favorite text editor:
>sudo nano /etc/dhcp3/dhclient.conf

seems to me there is an error here because /etc/dhcp3/dhclient.conf != /etc/resolve.conf


also it did not work for me

Thank you for pointing this out. I've updated the wiki.

You may have to restart your networking (or reboot) before these settings will take effect.

[brnetonboy]

The wiki says

Unless your ICS gateway can also perform DNS, you must manually configure the client with your ISP DNS servers. If you do not know your ISP's DNS servers, you can use OpenDNS servers instead.

all three of these options fail.

• Option 1: "Perform DNS." The link is to the Wikipedia entry on DNS. Not very helpful, I still have no idea whether or not my computer can do this or how to set it up. So I give up and move on.
  
• Option 2: "ISP DNS servers." What are those??!! How do I find out what my ISP DNS servers are? I searched the internet to no avail.
  
• Option 3: "use OpenDNS." The link to a very helpful step-by-step is great, however, I get stuck on step 3, as no connection shows up. In fact, Network Manager has a little X by it like I have no connection (though I do now have a connection, having gone through the ICS steps). Actually, the client computer is Ubuntu Studio, and it didn't even have Network Manager installed by default, so I had to install it and reboot (which deleted my connection and I had to do it all over again.)

So I definitely think the Wiki should be updated in this part, with more info on how people can pursue these different options.

----
PS: Please help me if you know the answers to these questions! I just want to have internet on my second computer! Thanks.

[brnetonboy]

Option 3: "use OpenDNS." The link to a very helpful step-by-step is great, however, I get stuck on step 3, as no connection shows up. In fact, Network Manager has a little X by it like I have no connection (though I do now have a connection, having gone through the ICS steps). Actually, the client computer is Ubuntu Studio, and it didn't even have Network Manager installed by default, so I had to install it and reboot (which deleted my connection and I had to do it all over again.)

I just had a thought... is it possible that the wiki wants me to configure OpenDNS on the Gateway, as opposed to the Client? The wiki does not specify. Which is it? I can easily follow the directions to install it on the Gateway computer. Please help! Then update the wiki to be more clear on this point.

[dmizer]

I just had a thought... is it possible that the wiki wants me to configure OpenDNS on the Gateway, as opposed to the Client? The wiki does not specify. Which is it? I can easily follow the directions to install it on the Gateway computer. Please help! Then update the wiki to be more clear on this point.

Nope, you'll have to configure OpenDNS on the client. It's under the client configuration settings so I thought it was clear enough. I'll take another look in a bit.

Your gateway AND client are both Ubuntu?

Edit: took another look at the wiki. This is what's currently written, and what you quoted earlier ->

Unless your ICS gateway can also perform DNS, you must manually configure the client with your ISP DNS servers. If you do not know your ISP's DNS servers, you can use OpenDNS servers instead.

Is there something about the wording that made you confused?

[brnetonboy]

Nope, you'll have to configure OpenDNS on the client. It's under the client configuration settings so I thought it was clear enough. I'll take another look in a bit.

Your gateway AND client are both Ubuntu?

You are probably right that it is clear enough but since I'm running into hurdles I started second guessing everything and thinking I must be doing something wrong.

Yes, both are Ubuntu. Gateway is Ibex 8.10, Client is Ubuntu Studio (8.10 as well).