[Gllug] arp problem?

[Ian Northeast]

Casper Gasper wrote:
> On 11/06/06, Adrian McMenamin <adrian at mcmen.demon.co.uk> wrote:
> 
>> On Sun, 2006-06-11 at 13:12 +0100, Casper Gasper wrote:
>> > > But the second box doesn't have an IP address, it just has a MAC
>> > > address. The box is booted with a very simple slave program which 
>> simply
>> > > loads loads the kernel into the right memory location and runs the
>> > > bootloader.
>> >
>> >  If it doesn't have an ip address, why are you attempting to ping it?
>> >
>>
>> Because the arp table ought to tell the kernel which MAC address to aim
>> for
> 
> 
>  That won't work, I've thought that in the past but it doesn't.  The
> arp table entry will send the packets to the machine, but when say a
> ping packet goes through the TCP/IP stack, it will get discarded
> because the destination IP address doesn't match the local ip -- or
> else, forwarded if ip forwarding is enabled on the machine.

It does with *some* devices, it's how we used to get an address onto 
Axis print servers. These interpret a ping sent to their MAC as an 
instruction to set the IP address to the one in the packet. This is 
enough to get onto the box with telnet/HTTP and configure the netmask, 
gateway etc.

I've not heard of Linux having this capability though, I'd have thought 
you'd need bootp/rarp.

Regards, Ian

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