[v6] Beginner with fixed-address6

Stephane Bortzmeyer bortzmeyer at nic.fr
Fri Jan 25 12:28:31 UTC 2008

On Fri, Jan 25, 2008 at 11:06:29AM +0000,
 Niall O'Reilly <Niall.oReilly at ucd.ie> wrote 
 a message of 36 lines which said:

> 	This is really broken, either in the specification (which I'll
> 	read one of these days)

The specification (RFC 3315) allows the client to put its hardware
address as a DUID (section 9.4). With this option, you have the same
behavior as in v4.

> or in the implementation.

ISC's DHCP client does not allow to use the "Link-layer Address"
(alone) DUID. But, anyway, a solution which depends on the client is
suboptimal since a DHCP server may expect many various clients.

> 	DHCP's main usefulness is in obviating (the cost of) a visit
> 	to the client.

At the present time, the only solution I see which fits this
requirment is to use tcpdump when the client boots to see its DUID and
then ask your favorite co-worker to write a Perl one-liner to
translate tcpdump's output to the syntax expected by ISC DHCP. (It
seems the server does not log the DUID.)

Remember also that it is only for fixed addresses (dynamic addresses
taken from a pool work fine).

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