The Ethernet Port

The Omega2 family devices feature a single 10/100M Ethernet integrated PHY. The addition of a transformer and a RJ45 port allow for quick and easy wired networking with ethernet cables.

The ethernet port can be configured to be a client or a DHCP host. It is set to client mode by default. Given the flexibility of the networking stack on the Omega2, there are a few overall modes of operation available:

  • Ethernet client - Omega obtains network access through a wired connection
  • Ethernet client + Router - Omega obtains network access through a wired connection and shares network access through its WiFi AP
  • Ethernet host - Omega provides IP addresses to a device connected to the ethernet port
  • Ethernet bridge - Omega obtains network access by connecting to a wireless network and shares network access to a device through ethernet

When using a through-hole Omega2 on a Dock with an Expansion Header, the Ethernet Expansion can be used to quickly add wired networking capabilities to the device. With custom hardware powered by the Omega2 or Omega2S, a transformer and an RJ45 port are required. See the Omega2S Reference Schematic for details.

Ethernet Client: Connecting to a Network through Ethernet

The Omega can join networks through a wired Ethernet connection, much like a desktop computer. By default, the Ethernet port on the Omega is configured to act as a network client, allowing users to simply plug in an ethernet cable and the Omega will do the rest: connecting to the network and attempting to obtain an IP address.

Note that by default, the Omega will have internet access. But it will not automatically share internet access to any devices connected to the Omega’s WiFi AP.

Enabling Ethernet Client Mode

As mentioned, the ethernet port is configured for ethernet client operation by default. However, if the configuration on your Omega has changed and you would like to quickly return to ethernet client mode, run the following command:

onion ethernet client

This will:

  • Configure the wan network interface to expect to obtain an IP address through DHCP
  • Remove any lan network interfaces
  • Remove any lan DHCP configurations

How Client Mode Works

For background, the Omega’s Ethernet interface is called eth0 by the system .

The default configuration in /etc/config/network defines a wan network interface that uses the physical eth0 interface, and expects to be given an IP address through DHCP.

Opening the /etc/config/network file, you will find a block that looks something like the following:

config interface 'wan'
   option ifname 'eth0'
   option proto 'dhcp'   

To learn more about OpenWRT’s network configuration, see the related OpenWRT network documentation.

Packet Routing

By default, the Omega’s firewall is not configured to share ethernet network access through the Omega’s WiFi Access Point.

If the goal is to share ethernet network access through the Omega’s WiFi Access Point, then the firewall configuration will need to be changed. Specifically, we will need to:

  • Add our wan network interface (that uses the eth0 ethernet interface) to the wan firewall rule
  • Update the wan firewall rule to allow packet forwarding

To do this, open the /etc/config/firewall file, find the block that looks something like:

config zone
        option name 'wan'
        option output 'ACCEPT'
        option forward 'REJECT'
        option masq '1'
        option mtu_fix '1'
        option network 'wwan'
        option input 'ACCEPT'

and do the following:

  • Change option forward 'REJECT' to option forward 'ACCEPT'
  • Change option network 'wwan' to list network 'wwan'
  • Add list network 'wan' after the list network 'wwan' line
config zone
        option name 'wan'
        option output 'ACCEPT'
        option forward 'ACCEPT'  # changed to ACCEPT
        option masq '1'
        option mtu_fix '1'
        list network 'wwan' # changed 'option' to 'list'
        list network 'wan'  # added wan network to list
        option input 'ACCEPT'

To learn more about OpenWRT’s firewall, see the related OpenWRT firewall documentation.

Ethernet Host: Acting as the Host on a Wired Network

Alternatively, the ethernet port can act as a host. Any devices connected to the ethernet port will receive an IP address - similar to when a device is connected directly to the ethernet ports on the back of a router.

Enabling Ethernet Host Mode

The ethernet port can be configured for host mode by running the following:

onion -t ethernet host
/etc/init.d/ethernet-mode disable
reboot

This will:

  • Remove the existing wan network interface that configures the ethernet port as a client
  • Creates a lan network interface that statically sets the IP address of that interface to 192.168.100.1
  • Creates a DHCP lan configuration that uses the lan network interfaces, and assigns any connected devices an IP address in the range of 192.168.100.100 to 192.168.100.150
  • Disable the ethernet-mode service that runs at boot to make sure the ethernet port is set to client mode

After your Omega reboots, the ethernet port will act as a host, assigning IP addresses to any connected devices.

How Host Mode Works

For background, the Omega’s Ethernet interface is called eth0 by the system .

After running the command above to enable ethernet host host mode, the configuration in /etc/config/network will define a lan network interface that uses the physical eth0 interface, and statically sets the IP address of that interface to 192.168.100.1

Opening the /etc/config/network file, you will find a block that looks something like the following:

config interface 'lan'
        option ifname 'eth0'
        option force_link '1'
        option macaddr '40:a3:6b:c0:27:84'
        option type 'bridge'
        option proto 'static'
        option ipaddr '192.168.100.1'
        option netmask '255.255.255.0'
        option ip6assign '60'

To learn more about OpenWRT’s network configuration, see the related OpenWRT network documentation.

DHCP

To be able to assign IP addresses to devices that connect to the ethernet port, there has to be a DHCP configuration. After running the command above to enable ethernet host host mode, the configuration in /etc/config/dhcp will define a lan DHCP configuration. It will be set up to assign IP address to connected devices in the range of 192.168.100.100 to 192.168.100.150 for 12 hour lease times.

About the assigned IP addresses: the base 192.168.100.* part comes from the lan network interface’s static IP address and netmask (set in /etc/config/network), and the range of 100 to 150 is configured here in the DHCP configuration.

Opening the /etc/config/dhcp file, you will find a block that looks something like the following:

config dhcp 'lan'
        option interface 'lan'
        option start '100'
        option limit '150'
        option leasetime '12h'
        option dhcpv6 'server'
        option ra 'server'

To learn more about OpenWRT’s DHCP configuration, see the related OpenWRT DHCP documentation.