## Contents * [1 Requirements](#Requirements) * [2 Installing](#Installing) * [3 Sharing via wired ethernet](#Sharing_via_wired_ethernet) * [3.1 Network bridge](#Network_bridge) * [4 Sharing via WLAN](#Sharing_via_WLAN) * [5 Sharing script](#Sharing_script) * [6 See also](#See_also) ## Requirements Before proceeding, you must make sure: 1. You must have a working PPP connection. 2. You must have an extra Ethernet interface card in your computer with which to share your connection. ## Installing The following packages must be [installed](/index.php/Pacman "Pacman") from the [official repositories](/index.php/Official_repositories "Official repositories") for both Wired and Wireless sharing: * [iptables](https://www.archlinux.org/packages/?name=iptables): for controlling packets in your network. * [dnsmasq](https://www.archlinux.org/packages/?name=dnsmasq): for acting as a DHCP and DNS caching server. * [bridge-utils](https://www.archlinux.org/packages/?name=bridge-utils): for setting up a network bridge. Depending on whether you want to share a wireless or wired connection, you also have to install: * **wired**: [iproute2](https://www.archlinux.org/packages/?name=iproute2) or [net-tools](https://www.archlinux.org/packages/?name=net-tools) (this article uses `iproute2` since `net-tools` is deprecated). * **wireless**: [iw](https://www.archlinux.org/packages/?name=iw) or [wireless_tools](https://www.archlinux.org/packages/?name=wireless_tools) (this article uses `iw` since `wireless_tools` is deprecated). ## Sharing via wired ethernet * Set the PPP connection up. You can assign an IP address to the interface as usual, by running (as root): ``` # ip addr add 192.168.0.254 dev eth0 ``` * Set the kernel to router mode. This is done by running: ``` # sysctl net.ipv4.ip_forward=1 ``` * Configure [dnsmasq](/index.php/Dnsmasq "Dnsmasq"). Make the following changes to `/etc/dnsmasq.conf` (uncomment if necessary): `/etc/dnsmasq.conf` ``` domain-needed bogus-priv interface=eth0 # change to your chosen interface dhcp-range=192.168.0.1,192.168.0.100,12h ``` * [Start](/index.php/Start "Start") the **dnsmasq** daemon. * Finally, set firewall to forward connections to and from the Internet for clients connecting to your WLAN. This is done by issuing: ``` # iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE ``` In the above the **ppp0** interface is the used PPP interface, you can substitute it for yours if needed. * You are done! Happy surfing! **Warning:** The previous configuration has no security options enabled. If you are using a firewall, you should adapt this documentation to suit your needs. Same applies also to setting up keys for WLAN interface. ### Network bridge Let's assume your PPP connection is on **eth0**, and you want to share the connection on **eth1** and **eth2**. ``` # ip addr add 0.0.0.0 dev eth1 # remove IP from eth0 # ip link set eth1 up # ensure the interface is up ``` ``` # ip addr add 0.0.0.0 dev eth2 # remove IP from eth1 # ip link set eth2 up # ensure the interface is up ``` ``` # brctl addbr br0 # create br0 node # brctl addif br0 eth1 # add eth0 to bridge br0 # brctl addif br0 eth2 # add eth1 to bridge br0 ``` ``` # ip addr add 192.168.0.254 dev br0 ``` change your interface in `dnsmasq.conf` to **br0**: ``` interface=br0 ``` and [restart](/index.php/Restart "Restart") the **dnsmasq** daemon. Now you should be able to connect to the internet using **eth1** or **eth2**. ## Sharing via WLAN **Warning:** These instructions create **unencrypted** ad-hoc network. See [Ad-hoc networking#WPA supplicant](/index.php/Ad-hoc_networking#WPA_supplicant "Ad-hoc networking") for method using WPA1 encryption. For better security, create an [access point](/index.php/Access_point "Access point") secured by WPA2. * Set up the PPP connection. * Set up the WLAN connection: choose an SSID and select Ad-hoc as network type. In the following it is assumed that you are using the **wlan0** interface. Set the **wlan0** interface up address for example 192.168.0.254\. Setting up the interface is usually done by running: ``` # iw wlan0 set type ibss # iw wlan0 ibss join MyFreeWlan ``` After that you can assign an IP address to the interface as usual, by running: ``` # ip addr add 192.168.0.254 dev wlan0 ``` Please note that different wlan cards may be configured differently and one should adapt this documentation accordingly. * Set the kernel to router mode. This is done by running: ``` # echo 1 > /proc/sys/net/ipv4/ip_forward ``` * Configure **dnsmasq**. Make the following changes to `/etc/dnsmasq.conf` (uncomment if necessary): `etc/dnsmasq.conf` ``` domain-needed bogus-priv interface=wlan0 # change to your interface dhcp-range=192.168.0.1,192.168.0.100,12h ``` * [Start](/index.php/Start "Start") the **dnsmasq** daemon. * Finally, set firewall to forward connections to and from the Internet for clients connecting to your WLAN. This is done by issuing: ``` # iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE ``` In the above the **ppp0** interface is assumed to be the used PPP interface, you can substitute it for yours if needed. * You are done! Happy surfing! **Warning:** The previous configuration has no security options enabled! If you are using firewall, you should adapt this documentation to suit your needs. Same applies also to setting up keys for wlan interface. ## Sharing script A quick script for sharing **eth0** over **wlan0** on an ad-hoc network. `ethoverwlan.sh` ``` #!/bin/bash iw wlan0 set type ibss iw wlan0 ibss join proxywlan ip addr add 192.168.0.254 dev wlan0 ip link set wlan0 up iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE echo 1 > /proc/sys/net/ipv4/ip_forward ``` ## See also * [Simple stateful firewall](/index.php/Simple_stateful_firewall "Simple stateful firewall") * [Router](/index.php/Router "Router") * [Wireless network configuration](/index.php/Wireless_network_configuration "Wireless network configuration") * [USB 3G Modem](/index.php/USB_3G_Modem "USB 3G Modem") * [Share your 3G Internet connection over wifi](http://go2linux.garron.me/linux/2011/03/share-your-3g-internet-connection-over-wifi-linux-ipod-touch-925)