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From: jny0 on 3 Jul 2010 14:31
I have an (embedded) linux device which is trying to communicate with
a URL (e.g. http://www.google.co.uk). When I wireshark the output
from the eth0, all I see is an ARP request for the default gateway,
which is never resolved. When I view the ARP table (arp, arp
neighbor, etc), Linux tells me it doesn't recognise the command.

This may be related, or may not. If I ty to ping an IP address, it
works fine. If I try to ping the URL associated with the IP address,
it doesn't. Sounds like a DNS problem. So, I checked /etc/
resolve.conf, but this is fine.

Other machines (admittedly, no embedded), don't have these problems.
Kernel was build using buildroot, and busybox, on a Fedora Linux
machine.
From: Tauno Voipio on 4 Jul 2010 05:32
On 3.7.10 9:31 , jny0 wrote:
> I have an (embedded) linux device which is trying to communicate with
> a URL (e.g. http://www.google.co.uk). When I wireshark the output
> from the eth0, all I see is an ARP request for the default gateway,
> which is never resolved. When I view the ARP table (arp, arp
> neighbor, etc), Linux tells me it doesn't recognise the command.

This means that the default gateway is not in the same physical
local network as your device, or your device is banned by the gateway.

Please note that in a network built of multiple local networks,
the default gateway is different in each local network. It is
the device connected to both the local network and to next
network towards the Internet.

> This may be related, or may not. If I ty to ping an IP address, it
> works fine. If I try to ping the URL associated with the IP address,
> it doesn't. Sounds like a DNS problem. So, I checked /etc/
> resolve.conf, but this is fine.

You do not get a connection to the DNS server, maybe of the
same problem as above.

> Other machines (admittedly, no embedded), don't have these problems.
> Kernel was build using buildroot, and busybox, on a Fedora Linux
> machine.

If you still have problems, please post the layout of
your network and the addresses, gateways and netmasks
assigned to each node.

--

Tauno Voipio
tauno voipio (at) iki fi

From: Chris Davies on 4 Jul 2010 12:25
jny0 <jny0(a)hotmail.com> wrote:
> I have an (embedded) linux device which is trying to communicate with
> a URL (e.g. http://www.google.co.uk). When I wireshark the output
> from the eth0, all I see is an ARP request for the default gateway,
> which is never resolved.

If the arp is not resolved then your embeeded device has not asked teh
right question, i.e. it's asking for an IP address that doesn't exist.

> When I view the ARP table (arp, arp
> neighbor, etc), Linux tells me it doesn't recognise the command.

This isn't clear to me. Do you mean that the embedded device doesn't have the "arp" command (or equivalent)? Does it have /proc

cat /proc/$$/net/arp


> This may be related, or may not. If I ty to ping an IP address, it
> works fine. If I try to ping the URL associated with the IP address,
> it doesn't.

You can't ping a URL - that's a semantically meaningless operation
Chris
From: jny0 on 5 Jul 2010 03:49

>     cat /proc/$$/net/arp
>
This gives me an ARP table (which includes a resolution fo rthe DNS),
but the DG is not present. By the way, what does the $$ bit of this
mean? cat /proc/net/arp seems to do the same thing.
From: Chris Davies on 5 Jul 2010 05:01
jny0 <jny0(a)hotmail.com> wrote:
> This gives me an ARP table (which includes a resolution fo rthe DNS),
> but the DG is not present.

OK, I would strongly suggest you go back to the networking configuration
and check that you really are using the correct IP address/netmask for
the gateway.


> By the way, what does the $$ bit of this mean? cat /proc/net/arp
> seems to do the same thing.

My mistake and disinformation on my part - I completely missed
/proc/net/arp, despite expecting something like it to be there.

Chris
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