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Re: Static IP distribution

  • From: Jay R. Ashworth
  • Date: Sun Jan 28 00:45:35 2001

On Sun, Jan 28, 2001 at 12:27:07AM -0500, Eric Sobocinski wrote:
> >Perhaps I'm misunderstanding either you, Eric, or the situation, but
> >DHCP client can supply a host name, can they not?  And I thought
> >servers could use that to look up for a fixed address.
> >
> >Yes, it's configurable, rather than fixed, but at least it's *there*.
> >
> >Would this not solve the gentleman's problem?
> Hmmm, you're right.  It gets supplied as a form of the "client identifier", 
> but I've never seen a host name used, and somehow I hadn't notice on my 
> recent reading of RFC 2131 that it even gives "DNS name" as an alternate 
> possible use of the "client identifier" option.  [RFC 2131, page 8 et 
> al]  I bow before your power of recollection.


Not bad, for my first day back after almost 2 years... 

> I'm left wondering how one would enforce correct configuration of host name 
> as the client identifier?  What would prevent one customer from configuring 
> a machine to steal someone else's static address?  That wouldn't be much 
> use for getting a second address but it would make for a dandy denial of 
> service against the "someone else".

You wouldn't, of course.  Such was the subtext of my comment on it
being "changeable".  But you can change some MAC addresses, too.

As for DOS in that context, short of PK authentication, you're probably
still SOL.

> I suppose that, as long as the client identifier can be arbitrary, that one 
> could issue a difficult-to-predict client identifier for each IP 
> address.  Tell the customer it's their IP address contract number?  You're 
> right, at least it's already there, even if the ISP discovers they have to 
> modify some DHCP client software in order to implement it.

:-)  I believe there's actually even an EditTheRegistry<tm> was to set
that on Win9x.

> (I'm humbled)

You do me too much honor, sir.

-- jra
Jay R. Ashworth                                                [email protected]
Member of the Technical Staff     Baylink
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