Setting up an off grid server, part 3. Networking.

I thought I would put up a few notes on networking on the Panda. When I originally purchased the device, it was my intention to use it as a home router. I would use a crossover cable on the built-in Ethernet to link to my desktop, and use the wi-fi adapter to act as a wireless access point for all the other machines in the house. The uplink is a topic for a different post, but it isn’t Ethernet based, wired or wireless.

The source that I would have used for that setup is here. https://help.ubuntu.com/community/WifiDocs/WirelessAccessPoint.

Unfortunately, while the hardware supports putting the wireless adapter into “master mode”, the current driver does not. It should around the 2.6.39 kernel, but that is about a year out on any Ubuntu Linux distro at this point. So for now, that idea is out and the current Linksys router stays.

I wanted to set up a static IP for my server, and I chose to do so by setting up a static DHCP entry in my router. The idea is like this. Normally when a computer is turned on in a network, it uses a protocol called DHCP to request a network address, and other information, so the user doesn’t need to worry about how to set it up every time. It’s a pretty good system and you’re most likely using it every day.

Now, one of the pieces of information in the request is the MAC Address. The MAC address is normally a hard-coded number that is unique to your one Ethernet interface. A typically laptop most likely has two, one on a wired port and one on the wireless. These are split between a manufacturer code and a serial number and no other device should ever have the same. Based on the MAC, some routers (like mine) can always give out the same IP address. This is refered to as a Static DHCP.

Unfortunately, the Panda is a little different, it always seems to set the mac address randomly on startup. This is a known oddity with the driver and will be fixed some point in the future, but for now it’s easy enough to work around.  I needed to edit the file /etc/network/interfaces which is used to set up the initial networking settings. There is an option to set up the mac address explicitly. Here is mine:

#start file
auto lo
iface lo inet loopback

#set the local ethernet to explicit dhcp
#and set the mac too, so that the router
#can assign the same ip everytime.
auto usb0
iface usb0 inet dhcp
 hwaddress ether 96:25:3C:B7:2E:41
#end file interfaces

Now I always grab my static IP on startup and my wife and use her little icon to find the files. To her, there is no difference between the old P4 and the new Panda.

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About Grant Wagner

General class ham: KC9SJQ https://grantwagner.wordpress.com
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