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

[Mirsad Goran Todorovac]

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, 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 at 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 at 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"; ddns-domainname "slava.alu.hr"; zone 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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