Hi Crist,

Thank you for your reply and the information provided.

I have roughly implemented this workaround. I was hoping there was a way to instruct BIND to masquerade a delegated domain with data from another (dynamically updated from ISC DHCP) zone.

More accurately, my (from upper level) mandated delegation is the literal 192/27.186.198.193.in-addr.arpa, using 192-27.186.198.193.in-addr.arpa says "ignoring records outside of the origin" or something like that.

I have used the following records in the zone:

$ORIGIN 192/27.186.198.193.in-addr.arpa.

@       IN      NS      domac.alu.hr.
@       IN      NS      bjesomar.srce.hr.

195     IN      PTR     test-record.slava.alu.hr.

$GENERATE 200-222 $ CNAME $.186.198.193.dhcp.

/etc/dhcp/dhcpd.conf has this:

  ddns-domainname "slava.alu.hr";
  ddns-rev-domainname "dhcp";
  zone slava.alu.hr. {
   primary 127.0.0.1;
   key DDNS_UPDATE;
  }
  zone 186.198.193.dhcp. {
   primary 127.0.0.1;
   key DDNS_UPDATE;
  }

However, don't I have to convince people managing bjesomar.srce.hr to be a slave server for the "186.198.193.dhcp" zone? Or the dynamically updated reverse PTR record will have effect only in my local domain (which I had even before the entire setup), won't it?

Also, I get spurious REFUSED or NXDOMAIN errors, some pass with time, so there must be some TTL or timeout.

Kind regards,

Mirsad

On 12/11/2021 6:04 AM, Crist Clark wrote:
No idea if this is the best way. It is a way.

Do you control any other zone? Let’s say you own “example.com.” You can tell ISC DHCP to build the reverse zone at an arbitrary base name instead of in-addr.arpa.

Configure DHCP to put the reverse records at say, “rev.example.com.” So you’ll get records at,

193.186.198.193.rev.example.com <http://193.186.198.193.rev.example.com>
194.186.198.193.rev.example.com <http://194.186.198.193.rev.example.com>
…

And in your RFC 2317-style delegation, you then enumerate another CNAME layer,

$ORIGIN 192-27.186.198.193.in-addr.arpa.
193  IN CNAME 193.186.198.193.rev.example.com <http://193.186.198.193.rev.example.com>. 194  IN CNAME 194.186.198.193.rev.example.com <http://194.186.198.193.rev.example.com>.
On Fri, Dec 10, 2021 at 2:51 PM Mirsad Goran Todorovac <mirsad.todoro...@alu.unizg.hr> wrote:

    Hello,

    I have a problem with DHCP DDNS update to BIND 9 reverse PTR zone
    subnet that is owned by several organizations, so I can't get a
    direct DHCP DDNS update access with a key or with hostname.

    I have been delegated domain name |192-27.186.198.193.in-addr.arpa
    from the upper level admins, and that appears to be immutable.|

    |However, my subnet is 193.198.186.192/27
    <http://193.198.186.192/27>, and DHCP only knows how to perform
    DDNS update to 186.198.193.in-addr.arpa. (See here:
    
https://serverfault.com/questions/806875/how-to-tell-isc-dhcp-correct-zone-for-reverse-zone-ddns-update
    and here:
    https://lists.isc.org/mailman/htdig/dhcp-users/2006-August/001422.html
    ).
    |

    |(This setup is because we have DHCP addresses that are not over
    NAT, but /24 subnet is shared with other organizations, even under
    another Minstry.)|

    |I want to have the effect of delegating the same database to
    upper level under their zone name, while updating the same
    database under my DHCP-understood zone name.|

    |I tried this /etc/bind/named.conf.local:|

    |zone "192-27.186.198.193.in-addr.arpa" in { type master; file
    "/var/cache/bind/192-27.186.198.193.in-addr.arpa.db"; }; zone
    "186.198.193.in-addr.arpa" in { type master; file
    "/var/cache/bind/192-27.186.198.193.in-addr.arpa.db"; allow-update
    { key DDNS_UPDATE; }; }; |

    (Two zones with the same file.)

    What I got was:

    |root@domac:/etc/bind# named-checkconf
    /etc/bind/named.conf.local:49: writeable file
    '/var/cache/bind/192-27.186.198.193.in-addr.arpa.db': already in
    use: /etc/bind/named.conf.local:44 root@domac:/etc/bind# Can you
    please tell me is there a way to achieve the effect of the above
    (illegal) setup? I can't change DHCP nor I know an option to tell
    it to accept update to |||192-27.186.198.193.in-addr.arpa| (it is a syntax 
error). The
    DHCP dhcpd.conf subnet configuration is: |||subnet 193.198.186.192 netmask 
255.255.255.224 { range
    193.198.186.200 193.198.186.222; # MT 20211210 option subnet-mask
    255.255.255.224; option domain-name-servers 161.53.235.3,
    161.53.2.70; option domain-name "slava.alu.hr
    <http://slava.alu.hr>"; ddns-domainname "slava.alu.hr
    <http://slava.alu.hr>"; zone slava.alu.hr <http://slava.alu.hr>. {
    primary 127.0.0.1; key DDNS_UPDATE; } zone
    186.198.193.in-addr.arpa. { primary 127.0.0.1; key DDNS_UPDATE; }
    option broadcast-address 193.198.186.223; option routers
    193.198.186.193; default-lease-time 43200; max-lease-time 86400; }
    | Thank you very much for your time reading this mail and help.
    Kind regards, -- Mirsad Goran Todorovac Academy of Fine Arts |
    Faculty of Graphic Arts University of Zagreb |

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