Network setup with NetworkManager

Bas Wijnen wijnen at
Fri Aug 12 04:18:45 EDT 2011

Xiangfu Liu schreef op vr 12-08-2011 om 08:07 [+0800]:
> we talk about the static MAC before, not settle down yet. I remember we talked something 
> in IRC(#qi-hardware at freenode) even multi same MAC address connect to one network, 
> will not cause any problem. 

Please be careful with your choice of words. A network is a physical
cable between two or more computers (possibly with hubs or switches in
between). Any computer on a network recognises any other computer on the
same network by its MAC address. It very much is a problem if two
computers on the same network share a MAC address.

However, this is irrelevant for the NanoNote. It uses usbnet, which is a
point-to-point protocol. This means that there are always exactly two
computers on the network.[1] These computers will not have the same MAC
address. And even if they do, it might still work, because the problem
is caused by two computers listening to the same data, and no computer
listens to its own data. But I'm not sure if there aren't checks in the
code which prevent sending data to the interface's own address.

What you mean is that it is possible to connect two NanoNotes to one
computer and give both NanoNotes the same Mac address. That is indeed
fine, because they aren't on the same network. The host computer has
usb0 and usb1, each of which is connected to one of the NanoNotes. The
computer will act as a router, possibly also as a masquerader. It allows
the different networks to communicate, but it doesn't turn them into one

Which brings us to the next point: it is possible to combine two
networks and make them look like one; this is called bridging. That will
most likely not work if there are two NanoNotes with the same MAC
address. This is not a problem. People who want to set up a bridge will
know what they're doing, and are capable of changing one of the MAC

> so I think we can use static MAC in future.

Indeed. :-)


[1] To make this even more clear: it is impossible to connect two
NanoNotes to one network, because it can only be connected to a USB
host, and both NanoNotes can only be USB device (or "function", as the
standard calls it).

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