[Testing] Actions: OLPC QA Call with Sri Lanka's Professional Volunteers

[Mitch Bradley]

Mikus Grinbergs wrote:
>> 7. Holt will SHIP 12 USB-to-Ethernet dongles from Boston to Sri Lanka.
>>     
>
> I have extensive experience at using Ethernet.  Please don't hesitate to
> ask me if you have questions.
>
>
> In the meantime, some things to keep in mind:
>
>  *  The XOs expect a name server to be available on that Ethernet (to
> give out dynamic IPv4 addresses).  The Ethernet ought to also have an
> NTP server on it.
>   

Nomenclature problem: Dynamic IPv4 addresses are given out by a DHCP 
server, not
a name server.  Name servers (also known as "DNS servers") translate 
textual names like
"dev.laptop.org" into numeric IP addresses; they have nothing at all to 
do with the assignment
of dynamic IPv4 addresses.

The symptom of a DHCP server problem is that machine cannot obtain an IP 
address for
itself - attempts to "bring up" the network interface will pause for a 
long time and
eventually time out.  The symptom of a name server problem is that the 
machine, after
the interface has already been brought up successfully, does not 
recognize the names
of machines on the outside Internet - you get messages like "unknown 
host" from commands
like "ping".

In some networks, the DHCP server program and the name server program 
happen to
be running on the same machine - a computer or a router box.  But that 
is not at all
necessary; they could be running on different machines in wildly 
different locations.
The DHCP server must be local - on the same Ethernet to as Mikus puts it 
- so your
machine can reach it by broadcasting, but the name server may be halfway 
around the world.

> [I myself have not yet tried running the Ethernet with IPv6 addresses.]
>
>  *  When you first install any XO (or first-boot any new build on that
> XO), do it without having the dongle plugged in at the XO.  You can plug
> the Ethernet connection in once you see any Sugar screen.
>
> What this does is assign the Ethernet device *after* the radio device
> has been assigned.  It turns out Ethernet control does not work well if
> 'eth0' had been assigned to the Ethernet device.  [ You can check that
> Ethernet is on 'eth1' in /etc/udev/rules.d/70-persistent-net.rules ]
>
> It helps if you keep the SAME Ethernet dongle with each individual XO.
> Each time you use a different dongle, Network Manager assigns a
> different interface name -- that can quickly get confusing.
>
>  *  The Network Manager could randomly step in and assign a zeroconf IP
> address to a working Ethernet interface (thereby taking the previously
> existing connection down).
>
> I actually wrote a tiny batch script that I invoke manually.  It issues
> the 'ifconfig' and 'route' commands to re-establish Ethernet connection.
>
>  *  If you boot and Ethernet is not working, issue 'ifconfig' and look
> for the (usually 'eth1') interface assigned to the Ethernet.  Network
> Manager is what assigns that interface - so it needs to be running.  A
> good way to "kick" the Ethernet connection into life (when the XO is
> running but the Ethernet isn't) is to unplug the Ethernet cable from the
> dongle, wait five or more seconds, then plug the cable back in again.
>
>  *  Attempts to assign a static IPv4 Ethernet address to an XO
> may/may_not work.  Tread carefully.
>
>  *  Treat the Ethernet icon in Frame more as an indicator than as a
> control over the Ethernet connection itself.  Instead:  to start
> Ethernet, plug in the cable;  to stop Ethernet, pull out the cable.
>
>
> mikus
>
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