dynamic dns - omitting duplicate names

[Barnaby Scott]

Glenn Satchell wrote:
> Hi Barnaby
> 
> I think you could handle this quite simply by creating a class, eg:
> 
> # perform dns updates for every client
> ddns-update-style interim;
> 
> # except those in this class
> class "music-players" {
>   match if option host-name = "musicplayer";
>   ddns-updates off;
> }
> 
> Alternatively you could assign a new ddns-hostname in the class,
> perhaps with a suffix containing part or all of the mac or ip address.
> 
> regards,
> -glenn

Thanks Glenn, that's beaut!

I feel a bit guilty because it's all there in man dhcpd.conf - I had 
read it, but it's only now that you show me how that the fog begins to 
clear!

What I wanted to achieve is now working perfectly, but if I may, I have 
one more query:

Given your lead, I tried to go one step further and use a substring, but 
that doesn't seem to work.

Copying yours, I now have:

class "music-players" {
   match if option host-name = "SonosZP";
   ddns-updates off;

However there is also a thing on the network calling itself a SonosCR. 
Though there is only one of these (+ multiple SonosZP's), the chances 
are there might be more than one in future. In trying to be clever and 
anticipate this I tried:

class "music-players" {
   match if substring (option host-name, 1, 5) = "Sonos";
   ddns-updates off;

but this doesn't work. Any idea why?

Many thanks again for your excellent answer.

Barnaby