Connecting to the world

Beagleblog

Controlling the Beagleboard over a serial line with a terminal program such as Minicom is working just fine, but it's much more convenient to have a real network connection. For instance to update the Linux distribtion on the SD card without having to unplug it and plug it into a PC's card reader. There's just one little obstacle to overcome: The board does not feature either an Ethernet port or a Wifi chip :)

Luckily the Linux kernel programmers are providing a solution to that problem for quite some time: You can use the USB interface for networking, too. So I just connect the Beagleboard to the computer with a USB cable in addition to the serial connection I am using to control the board. There's no need to load a kernel module or compile special software for this to work. The only thing left is to enter the following line into the terminal that connects to the board:

root@beagleboard:~# /sbin/ifconfig usb0 192.168.0.2 netmask 255.255.255.0

The same goes for the PC, just with a different address:

# /sbin/ifconfig usb0 192.168.0.1 netmask 255.255.255.0

That's enough to have a working connection between Beagleboard and PC, as you can see with the ping command:

$ ping 192.168.0.2
  PING 192.168.0.2 (192.168.0.2) 56(84) bytes of data.
  64 bytes from 192.168.0.2: icmp_seq=1 ttl=64 time=0.203 ms
  64 bytes from 192.168.0.2: icmp_seq=2 ttl=64 time=0.207 ms
  ...

To get on the Internet you need to configure your PC as the default router and set up Network Address Translation (NAT) accordingly. Setting the default route on the board is as simple as:

  root@beagleboard:~# route add default gw 192.168.0.1

The following commands will configure Masquerading on the PC and activate IP routing in the Linux kernel:

# iptables --table nat --append POSTROUTING --out-interface wlan0 -j MASQUERADE
    # iptables --append FORWARD --in-interface usb0 -j ACCEPT
    # echo 1 > /proc/sys/net/ipv4/ip_forward

Beware that I am using "wlan0" here as the outgoing interface, as my PC has a wireless connection to the Internet. Depending on the brand of hardware you might need to write "wmaster0" here, or just "eth0" if you are using an Ethernet connection.

To conveniently make use of host names instead of plain IP addresses you need to add the IP address of a nameserver to the Beagleboard's "/etc/resolv.conf" configuration file. If it's working you can start an update of the Angstrom distribution with "opkg update".

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