help with dhcp custom options

[Glenn Satchell]

I haven't used the ISC dhclient very much, but I think you need to add 
the special-purpose option to the request list. I know the server will 
only send those options the client asks for.

regards,
-glenn

On 05/28/11 04:30, Robert Schweikert wrote:
> I suppose this is rather frequently discussed topic as I found many
> threads with this topic, yet I was still not able to figure out an
> answer to my question. Thus, help is much appreciated.
>
> I need to identify a DHCP server for a specific purpose and then set up
> clients to look for this specific DHCP server while refusing lease
> offers from other DHCP server that my be on the network. My idea was to
> do this via a custom option.
>
> I have the following dhcpd.conf file:
>
> option rfc3442-classless-static-routes code 121 = array of unsigned
> integer 8;
> option domain-name "mydomain";
> max-lease-time 7200;
> # Custom option to identify this DHCP server as the cloud DHCP server
> # Define the new option
> option special-purpose code 239 = ip-address;
> # Set the value
> option special-purpose 192.168.1.2;
> # Set the address range to be handed out.
> subnet 192.168.1.0 netmask 255.255.255.0 {
> range 192.168.1.5 192.168.1.10;
> default-lease-time 86400000;
> max-lease-time 1728000000000;
> }
>
> And on the client side I have dhclient.conf
>
> option rfc3442-classless-static-routes_raw code 121 = array of unsigned
> integer 8;
>
> # Request several well known/usefull dhcp options.
> request subnet-mask, broadcast-address, routers,
> rfc3442-classless-static-routes_raw,
> interface-mtu, host-name, domain-name,
> domain-name-servers, nis-domain, nis-servers,
> nds-context, nds-servers, nds-tree-name,
> netbios-name-servers, netbios-dd-server,
> netbios-node-type, netbios-scope, ntp-servers;
>
> # We request above options, require only the IP configuration:
> require subnet-mask;
> # All another options (DNS, NTP, NIS, ...) are applied using
> # netconfig(8) modules.
>
> # To enforce the availability of the dns server list, set to:
> #require subnet-mask, domain-name-servers;
>
> timeout 60;
> retry 60;
> reboot 10;
> select-timeout 5;
> initial-interval 2;
>
> option special-purpose code 239 = ip-address;
> require special-purpose;
>
>
> With the dhcp server running on machine A (not startup messages or
> errors) and rge dhclient running on machine B, I get complaints that the
> server is not offering the "special-purpose" option. Thus the lease is
> not being accepted.
>
> How do I get the server to send the option?
>
> Or am I going about this the wrong way and I should do this differently?
>
> Thanks,
> Robert
>