Dynamic client host-name (Option 12)

[Bill Shirley]

I use fqdn.fqdn:
subnet 192.168.4.0 netmask 255.255.255.0 {
     ddns-updates            on;
     ddns-domainname         "example.com";
     option domain-name      "example.com";
     option fqdn.fqdn        = concat(config-option server.ddns-hostname, ".", config-option server.ddns-domainname);

You didn't post hw_mac_short.  You could use something like this:
ddns-hostname = concat("mta-", binary-to-ascii(16, 8, "", substring(hardware, 4, 3)));
This uses the last three bytes of the MAC address. Put this before the subnet definition.

Bill

On 8/30/2019 4:06 PM, Dave M wrote:
> I have clients (eMTA) who request a hostname parameter. It is easy to create static entries and provide clients with an 
> hostname back but I can't manage to do it dynamically.
>
> I have the rest of my configuration working fine except that one line:
>
>         subnet 172.16.52.0 netmask 255.255.254.0
>         {
>                 allow leasequery;
>                 option routers 172.16.53.254;
>                 option broadcast-address 172.16.53.255;
>                 option domain-name-servers 172.16.64.15 ;
>                 ddns-hostname = concat("mta-", hw_mac_short);
>                 ddns-domainname "emta.lab.com <http://emta.lab.com>.";
>                 host-name = concat("mta-", hw_mac_short); -----> not working
>                 option domain-name "emta.lab.com <http://emta.lab.com>";
>                 filename = concat("config/mta-", hw_mac_short, ".cfg");
>                 pool
>                 {
>                         #pool: MTA 172.16.52.1 172.16.53.253
>                         range 172.16.52.1 172.16.53.253;
>
>                         allow members of "MTA";
>                 }
>         }
>
> If I hardcode the host-name, then the DDNS works fine and gets created based on the mac (variable hw_mac_short) but I can't 
> figure out how to return option 12 dynamically to clients requesting it.
>
> I'm testing this on ISC DHCP 4.4.1
>
> Is there a trick for that?
>
> Dave M.
>
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