[SOLVED] Can I use iptables to share a wireless connection

baronobeefdip · 01-02-2014, 06:11 PM

I am trying to make a router with a spare computer I have in the house. I basically want to use the spare computer to receive the wireless connection and then route it to the ethernet cable. I want to be able to connect a device to the internet from it's ethernet cable to the machine and for the machine it's connected to to receive the internet connection through it's wireless interface.

I read that this can be done with iptables, The many guides I have read give vague details and steps on how to do it but doesn't explain what the commands do. I appreciate the help.

custangro · 01-02-2014, 06:55 PM

Well I don't know what distro of Linux you're using...but in "Red Hat Land"

Enable packet forwarding in /etc/sysctl.conf

Code:

net.ipv4.conf.default.forwarding=1

Load in sysctl settings from /etc/sysctl.conf

Code:

sysctl -p

Then set up IP tables to route the traffic...

Code:

service iptables stop
iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE
service iptables save
service iptables restart

Then set your client machines' default gateway address to the address of eth0 (or whatever your wired network is) of the server

schneidz · 01-02-2014, 07:04 PM

this is what i do:
http://www.linuxquestions.org/questi...6/#post3804866

baronobeefdip · 01-02-2014, 07:52 PM

Just to make things clear just so I know I am getting the information right. This is going to allow my machine to receive internet connection wirelessly and then route the traffic to the ethernet port on the machine I am playing with. Plus I am having some trouble with the DHCP server at the moment but that is for another thread.

by the way , I did enable forwarding in the kernel but then I ran the command that you told me to run in the post you posted and got these errors.

Code:

error: "net.bridge.bridge-nf-call-ip6tables" is an unknown key
error: "net.bridge.bridge-nf-call-iptables" is an unknown key
error: "net.bridge.bridge-nf-call-arptables" is an unknown key

And here is the configuration files for each of the interfaces.
ifcfg-eth0

Code:

DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
NETWORK=10.0.0.0
NETMASK=255.255.255.0
IPADDR=10.0.0.1

ifcfg-wlan0

Code:

DEVICE=wlan0
BOOTPROTO=dhcp
ONBOOT=yes

dhcpd.conf

Code:

option domain-name "baronobeefdip.josh";
option domain-name-servers 10.0.0.1, 8.8.8.8;
subnet 10.0.0.0 netmask 255.255.255.0 {
range 10.0.0.2 10.0.0.254;
option routers 10.0.0.1;
option broadcast-address 10.0.0.255;
}

baronobeefdip · 01-02-2014, 08:17 PM

UPDATE:

My DHCP server it working, Now I just need to get the routing portion of everything working. I ran the commands that were inside of the code box with regards to iptables.

Code:

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

I connected to the machine through the ethernet port and DHCP caught an IP like it should but then I tried to nslookup google and it returned an error. Something still isn't working here. What do you think it is? My guess is this error

Code:

error: "net.bridge.bridge-nf-call-ip6tables" is an unknown key
error: "net.bridge.bridge-nf-call-iptables" is an unknown key
error: "net.bridge.bridge-nf-call-arptables" is an unknown key

What causes these errors. I know it's a redhat thing but I want to know if this is an issue with the routing rules in iptables.

baronobeefdip · 01-02-2014, 09:11 PM

I just got everything working. I went by the iptables rules at this link
http://www.yolinux.com/TUTORIALS/Lin...rkGateway.html

baronobeefdip · 01-07-2014, 07:49 PM

One last thing I want to know here, Can I do this without turning the computer into a router? I know that using the rule

Code:

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

Will turn it into a router. It's creating a seperate broadcast domain which I don't want. I want to make it to where the clients connected to the ethernet interface could be a part of the same broadcast domain coming from the wireless router in the house. I don't want to turn this machine into a router because I want the entire network of clients connected to it to be part of the same broadcast domain as everyone else.
I thought about doing some experimentation with this so I made these rules

Code:

iptables -A FORWARD -i eth0 -j ACCEPT
iptables -A FORWARD -o eth0 -j ACCEPT
iptables -A FORWARD -i wlan0 -j ACCEPT
iptables -A FORWARD -o wlan0 -j ACCEPT

And when I tried to make the eth0 interface obtain an IP address from the router it did't get one. the wlan0 interface has an IP address and forwarding is enabled but I don't know how to make eth0 get an IP address from the router. Can someone help me with this one. I am understanding the relavance of the FORWARD chain and most of the chains in the nat table but the nat table seems to be creating a router and not a bridge so that the clients attached to it can join the same broadcast domain as the ones connected to the router that the machine is wirelessly connected to.