DNS Classless delegation

This is the method by which we can allocate a group of addresses less than the whole class C address ( for 254 machines ).

The machine owning the parent domain will be primary for the class C, and will hold the data records for it. The data records on this machine will not resolve the address to a name. It will instead have a CNAME for the address pointing to the machine controlling that small section of addresses.
The machine controlling the addresses will then have a similar data file resolving the names to addresses.

Please see the examples below for the implementation specifics.

In this example the reverse domain that we are splitting up is an imaginary one 10.11.12.x

Primary Server

This is the machine that will be authorative for the class C address. It will have records for all of the addresses within that class C, but instead of resolving them to a name, it will point to the machine that is running the range of addresses.

We will be splitting it up to pass off the first five addresses to a domain run by the 8hjorta machine. The addresses 193 to 197 will be run by the 8purrii machine that is running the reverse domain. There would of course be no problems with sending different bits of the domain to different machines, but for ease of understanding we only show one remote machine, and the primary server.

Named.boot file

;
; NAMED.BOOT file for name server configuration.
;
; type       domain                      source file or host
;
directory    /var/named

cache        .                           named.ca

primary      0.0.127.in-addr.arpa        named.local

primary      portsmouth.uk.ibm.com       primary/portsmouth.data
primary      151.180.9.in-addr.arpa      primary/9.180.151.rev

primary      parent.top                  primary/parent.top.data
primary      12.11.10.in-addr.arpa       primary/10.11.12.rev

Reverse domain file

primary/10.11.12.rev

;*************************************
;*    Start of Authority Records     *
;*************************************
;
@        IN  SOA  8purrii.portsmouth.uk.ibm.com.  dnsadmin.8purrii.portsmouth.u
k.ibm.com. (
1996071701; Serial number for this data (yymmdd##)
  86400    ; Refresh value for secondary name servers (1 day)
  3600     ; Retry value for secondary name servers   (1 hour)
  604800   ; Expire value for secondary name servers  (42 days)
  86400 )  ; Minimum TTL value (7 days)
;
; Define Name Servers
;
IN  NS    8purrii.portsmouth.uk.ibm.com.

sub1-5  IN  NS  8hjorta.portsmouth.uk.ibm.com.

;
; Define Hosts in this domain 
;
1       IN   CNAME   1.sub1-5.12.11.10.in-addr.arpa.
2       IN   CNAME   2.sub1-5.12.11.10.in-addr.arpa.
3       IN   CNAME   3.sub1-5.12.11.10.in-addr.arpa.
4       IN   CNAME   4.sub1-5.12.11.10.in-addr.arpa.
5       IN   CNAME   5.sub1-5.12.11.10.in-addr.arpa.


193     IN   PTR   mum.parent.top.
194     IN   PTR   dad.parent.top.
195     IN   PTR   martha.parent.top.
196     IN   PTR   michelle.parent.top.
197     IN   PTR   brian.parent.top.

Forward data file

primary/parent.top.data

;*************************************
;*    Start of Authority Records     *
;*************************************
;
@        IN  SOA  8purrii.portsmouth.uk.ibm.com.  dnsadmin.8purrii.portsmouth.uk
.ibm.com. (
        1996071701; Serial number for this data (yyyymmdd##)
          14400    ; Refresh value for secondary name servers (2 hours)
          3600     ; Retry value for secondary name servers   (1 hour)
          604800   ; Expire value for secondary name servers  (7 days)
          86400 )  ; Minimum TTL value   (1 day)
;
; Define Name Servers
;
                IN    NS    testdomain.parent.top.
;
; Define Hosts in this domain
;
mum.parent.top.         IN  A  10.11.12.193
dad.parent.top.         IN  A  10.11.12.194
martha.parent.top.      IN  A  10.11.12.195
michelle.parent.top.    IN  A  10.11.12.196
brian.parent.top.       IN  A  10.11.12.197

Secondary Server

Will be set up in a very similar manner to the primary.
Normal differences.

Named.boot file

Class reverse file
Forward data file
Reverse data file

Control Server ( Customers machine)

Named.boot file

;
; NAMED.BOOT file for name server configuration.
;
; type          domain                          source file or host
;

directory       /var/named

cache           .                               named.ca

primary         0.0.127.in-addr.arpa            named.local

secondary       portsmouth.uk.ibm.com   9.180.151.79    primary/portsmouth.data
secondary       151.180.9.in-addr.arpa  9.180.151.79    primary/9.180.151.rev

secondary       12.11.10.in-addr.arpa   9.180.151.79    primary/10.11.12.rev

primary         child.domain                    primary/child.data
primary         sub1-5.12.11.10.in-addr.arpa    primary/sub1-5.rev

Forward data file

Reverse domain file

;*************************************
;*    Start of Authority Records     *
;*************************************
;
@        IN  SOA  8hjorta.portsmouth.uk.ibm.com.  dnsadmin.8hjorta.portsmouth.uk
.ibm.com. (
        1996071701 ; Serial number for this data (yymmdd##)
          86400    ; Refresh value for secondary name servers (1 day)
          3600     ; Retry value for secondary name servers   (1 hour)
          604800   ; Expire value for secondary name servers  (42 days)
          86400 )  ; Minimum TTL value (7 days)
;
; Define Name Servers
;

        IN  NS  8hjorta.portsmouth.uk.ibm.com.
;
; Define Hosts in this domain 
;
1       IN   PTR   teddy.child.domain.
2       IN   PTR   batrobin.child.domain.
3       IN   PTR   charlie.child.domain.
4       IN   PTR   daisy.child.domain.
5       IN   PTR   elly.child.domain.