Date: Tue, 23 Nov 2004 19:57:41 -0500 (EST)
From: linux-os <linux-os@chaos.analogic.com>
Reply-To: linux-os@analogic.com
To: "Pedro Venda (SYSADM)" <pjvenda@rnl.ist.utl.pt>
cc: linux-kernel@vger.kernel.org
Subject: Re: Running Ethernet without ARP
In-Reply-To: <41A3634D.6050108@rnl.ist.utl.pt>
Message-ID: <Pine.LNX.4.61.0411231948200.11065@chaos.analogic.com>
References: <20041123140025.GA32447@beton.cybernet.src>
 <Pine.LNX.4.61.0411230937140.4513@chaos.analogic.com> <41A3634D.6050108@rnl.ist.utl.pt>
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On Tue, 23 Nov 2004, Pedro Venda (SYSADM) wrote:

> linux-os wrote:
>> On Tue, 23 Nov 2004, Karel Kulhavy wrote:
>> 
>>> Hello
>>> 
>>> man netdevice says:
>>> "IFF_NOARP    No arp protocol, L2 deswtination address not set".
>>> Is it possible to run ptp Ethernet link between two Linux routers this
>>> way? I would like to run the link with two constraints:
>>> 1) no ARP protocol used
>>> 2) The link should continue to work even if root access to one computer is
>>> inaccessible and the NIC in the other one is replaced without changing
>>> it's MAC (for example because it doesn't support MAC change)
>>> 
>>> Cl<
>> 
>> 
>> ARP means address resolution protocol. That's how one machine
>> learns about the MAC (Hardware) address of another so it can
>> communicate with it. Without ARP, you need to send / receive
>> broadcast packets (Like M$ Netboius). This means that everything
>> is received by everyone on the LAN and needs to be dumped on
>> the floor by everybody except the intended target.
>
> or somehow a static table can be built.
> not sure what the point would be, but I cannot see anything that would make 
> it impossible.
>
> regards,
> pedro venda.
>

Of course you could do the monkeys on the keyboard thing and
eventually have something that shows it's not impossible. The
problem is that an IP address needs to be associated with that
hardware address. ARP is fundamental for any peer-to-peer
communication on Ethernet. Its even used in DECNET and NETBIOS,
although called RIP.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.9 on an i686 machine (5537.79 BogoMips).
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