RE: [dhcwg] Trust model of Client FQDN option

"Bernie Volz" <> Wed, 04 August 2004 00:55 UTC

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From: "Bernie Volz" <>
To: "'Ted Lemon'" <>, "'Pekka Savola'" <>
Subject: RE: [dhcwg] Trust model of Client FQDN option
Date: Tue, 3 Aug 2004 20:39:25 -0400
Organization: Cisco
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Also, it is generally viewed as a bad idea to mix both static and dynamic
DNS resource records in a zone. So, if you want to completely avoid the
problem, keep the zones which contain the administrative DNS information
(www., ftp., pop3., ...) separate from the (dynamic) client information.

- Bernie

> -----Original Message-----
> From: [] 
> On Behalf Of Ted Lemon
> Sent: Tuesday, August 03, 2004 6:19 PM
> To: Pekka Savola
> Cc:
> Subject: Re: [dhcwg] Trust model of Client FQDN option
> On Aug 3, 2004, at 11:03 AM, Pekka Savola wrote:
> > I'm not sure the v4 or v6 DHC FQDN client options address 
> the problem 
> > of the trust model for the update content sufficiently 
> well.  I'd even 
> > go as far to say that it might create a false sense of security.
> Pekka, in the meeting this morning, you said you hadn't read 
> the drafts 
> having to do with DNS updates on DHCPv4.   Have you now read them?   
> The reason I ask is that for the entire duration of the time 
> I've been 
> coming to IETF, people have occasionally raised the very same 
> issue you 
> are now raising.
> The solution we have adopted, which is widely deployed, allows two 
> answers to your question.   The first is a more paranoid 
> solution that 
> requires widespread distribution of individual DNS update keys.   The 
> second is a more laissez-faire solution that does not require the 
> distribution of individual DNS update keys.   This second solution is 
> no more or less secure than the first, but its behavior is 
> different.   
> Names added by the DHCP server are marked as such, and if a name is 
> present and was not added by the DHCP server, that name can't be 
> replaced at the request of the DHCP client.   When a client's lease 
> expires, another client can acquire the previous client's name, so 
> there's no protection for client names.   You get to pick which 
> solution to deploy, based on your willingness to distribute keys and 
> based on whether or not you care whether a DHCP client can count on 
> retaining its name, once its name is registered.
> So this is a well-understood problem, with well-understood and widely 
> deployed solutions.   You can see an example implementation 
> in the ISC 
> DHCP client and server if you're curious, and as far as I know every 
> commercial DHCP server also implements this, and I know of 
> quite a few 
> sites that use it in practice.  Indeed, it's been deployed at IETF 
> meetings in the past (not sure if it's running this time).
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