ISC-DHCP and BIND 9 DNS: DDNS update fails for /27 subnet

Question

I have a problem with DDNS update with ISC-DHCP server.

My /etc/dhcp/dhcpd.conf subnet section that doesn't work 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";
  ddns-domainname "slava.alu.hr";
  zone slava.alu.hr. {
   primary 127.0.0.1;
   key DDNS_UPDATE;
  }
  zone 192-27.186.198.193.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;
}

My network delegation for my 193.198.186.192/27 is a literal 192/27.186.198.193.in-addr.arpa. and they do not appear willing to change it.

See here:

root@domac:~# host -t any 193.198.186.195
195.186.198.193.in-addr.arpa is an alias for 195.192/27.186.198.193.in-addr.arpa.
195.192/27.186.198.193.in-addr.arpa domain name pointer test-record.slava.alu.hr.
root@domac:~#

This mandates my /etc/bind/named.conf.local entry to:

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";
        allow-update { key DDNS_UPDATE; };
};

However, ISC DHCPd considers an "/" in zone name a syntax error.

Is there a way to tell to either BIND or ISC DHCPd to accept different names in /etc/bind/named.conf.local and /etc/dhcp/dhcpd.conf zone declarations?

When I change declaration in dhcpd.conf to:

  zone 186.198.193.in-addr.arpa. {
   primary 127.0.0.1;
   key DDNS_UPDATE;
  }

and /etc/bind/named.conf.local entry to:

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; };
};

then dynamic DHCPd update works:

Dec 10 15:42:59 domac dhcpd[11512]: DHCPREQUEST for 193.198.186.211 from e8:48:b8:5b:8c:46 (LAPTOP-MTODOROV) via 193.198.186.193
Dec 10 15:42:59 domac dhcpd[11512]: DHCPACK on 193.198.186.211 to e8:48:b8:5b:8c:46 (LAPTOP-MTODOROV) via 193.198.186.193
Dec 10 15:42:59 domac dhcpd[11512]: Added new forward map from LAPTOP-MTODOROV.slava.alu.hr to 193.198.186.211
Dec 10 15:42:59 domac dhcpd[11512]: Added reverse map from 211.186.198.193.in-addr.arpa. to LAPTOP-MTODOROV.slava.alu.hr

and I can see it from my DNS server's realm:

root@domac:~# host laptop-mtodorov.slava.alu.hr
LAPTOP-MTODOROV.slava.alu.hr has address 193.198.186.211
root@domac:~# host -t any 193.198.186.211
211.186.198.193.in-addr.arpa domain name pointer LAPTOP-MTODOROV.slava.alu.hr.
root@domac:~#

... but now the DNS delegation is broken. I can't possibly have the entire 186.198.193.in-addr.arpa. zone for our domain's subnet, and neither will they approve dynamic updates on the central DNS server.

I can't seem to have both, unless there is a way to instruct DHCP or BIND to add to a zone with a different name in BIND from that in DHCP.

I seem to be running out of options.

Thank you very much if you know an answer.

Kind regards, Marvin

P.S.

I have tried the following and it did not work:

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#

Nice try :-( The programmers were clever enough to prevent this hack!

Any idea how to make two zones refer to the same zone database, one that would match the assigned delegation zone, and the other that would match the 186.198.193.in-addr.arpa zone that ISC DHCP only knows how to update?

2. I have even tried to enclose 192/27.186.198.193.in-addr.arpa in quotes to avoid the syntax error, and I got this:

   Dec 10 23:17:45 domac dhcpd[26555]: /etc/dhcp/dhcpd.conf line 187: expecting hostname. Dec 10 23:17:45 domac isc-dhcp-server[26545]: /etc/dhcp/dhcpd.conf line 187: expecting hostname. Dec 10 23:17:45 domac isc-dhcp-server[26545]: zone "192/27.186.198.193.in-addr.arpa." Dec 10 23:17:45 domac isc-dhcp-server[26545]: ^ Dec 10 23:17:45 domac isc-dhcp-server[26545]: Configuration file errors encountered -- exiting Dec 10 23:17:45 domac isc-dhcp-server[26545]: exiting. Dec 10 23:17:45 domac dhcpd[26555]: zone "192/27.186.198.193.in-addr.arpa."

So, this didn't work either. The only hope is finding a way to use the same DNS zone database with two zone names. That isn't so rare case I suppose, there should be a provision for such case?

Marvin