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By creating reverse lookup zones for each IP subnet, you gain a robust database that can be used to track
assignments within an IP address space. Reverse lookups can determine the allocation status of any
address from any DNS client.
Network operators must account for used and unused IP addresses. It is recommended that each IP
address be given a DNS PTR Resource Record, even if the address is unused. For example, you can look
up and resolve an IP address as "unused-XXX.the.net."
See the following example to create a zone from a BIND file by entering the zone command:
nrcmd> zone 101.21.172.in-addr.arpa. create primary file=the.net_rev_zone.txt
The following edited BIND definition file is for "the.net_rev_zone.txt."
@
esupport-austin.the.net. (
;
;
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
(Truncated for brevity..)
253
254
255
For a sample BIND file that can be used as a template and edited for your environment, go to
http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/dialnms/bindtemp.txt
IN
SOA
onionring.the.net
2000071600
3600
1800
86400
86400
)
IN
NS
onionring.the.net.
IN
PTR
broadcast-0.the.net.
IN
PTR
unused-1.the.net.
IN
PTR
unused-2.the.net.
IN
PTR
unused-3.the.net.
IN
PTR
unused-4.the.net.
IN
PTR
unused-5.the.net.
IN
PTR
unused-6.the.net.
IN
PTR
unused-7.the.net.
IN
PTR
unused-8.the.net.
IN
PTR
unused-9.the.net.
IN
PTR
unused-10.the.net.
IN
PTR
unused-11.the.net.
IN
PTR
unused-12.the.net.
IN
PTR
unused-13.the.net.
IN
PTR
unused-14.the.net.
IN
PTR
unused-15.the.net.
IN
PTR
unused-16.the.net.
IN
PTR
unused-17.the.net.
IN
PTR
unused-18.the.net.
IN
PTR
unused-19.the.net.
IN
PTR
doc-rtr58-01.the.net.
IN
PTR
doc-rtr54-01.the.net.
IN
PTR
doc-rtr53-01.the.net.
IN
PTR
doc-rtr53-01.the.net.
IN
PTR
unused-253.the.net.
IN
PTR
unused-254.the.net.
IN
PTR
broadcast-255.the.net.
; serial number
; Refresh 1 hours
; Retry 30 minutes
; Expire 24 hours
; TTL 24 hours
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