Hostname and DNS

[Glenn Satchell]

>Subject: Hostname and DNS
>Date: Wed, 30 May 2007 15:17:10 +0200
>From: "Lars Jacobsen" <lj at sydfynsel.dk>
>To: <dhcp-users at isc.org>
>
>Is it possible to set/force the client-hostname to ie. Opt.82 CID ?
>Or another way to update DDNS to circuitID.example.org
>
>Example this lease:
>
>lease 85.27.135.233 {
>  starts 3 2007/05/30 12:08:20;
>  ends 3 2007/05/30 13:08:20;
>  binding state active;
>  next binding state free;
>  billing subclass "2115-ch2" "2115192";
>  hardware ethernet 00:03:2f:20:00:1c;
>  uid "\001\000\003/ \000\034";
>  option agent.circuit-id "2115192";
>  client-hostname "802.11b Wireless Router";
>
>I would like the DNS to be: "2151192.example.org" not "802.11b Wireless
>Router.example.org"

Something like this in an appropriate scope:

  ddns-hostname = option agent.circuit-id;
  
or use pick-first-value() in case the circuit-id is not set:

  ddns-hostname = pick-first-value(
        option agent.circuit-id,
        option host-name,
        binary-to-ascii (16, 8, "-", substring (hardware, 1, 6)) );

This is from the dhcpd.conf man page:

SETTING PARAMETER VALUES USING EXPRESSIONS
     Sometimes it's helpful to be able to set the value of a DHCP
     server  parameter  based  on  some value that the client has
     sent.   To do this, you can use expression evaluation.   The
     dhcp-eval(5) manual page describes how to write expressions.
     To assign the result of an evaluation to an  option,  define
     the option as follows:

       my-parameter = expression ;

     For example:

       ddns-hostname = binary-to-ascii (16, 8, "-",
                                        substring (hardware, 1, 6));

regards,
-glenn