Cisco CNS Network Registrar User's Guide, 5.5
Appendix: Resource Records
Downloads: This chapterpdf (PDF - 210.0KB) The complete bookPDF (PDF - 5.45MB) | Feedback

Resource Records

Table Of Contents

Resource Records


Resource Records


Resource records comprise the data within a DNS zone. There is no fixed limit to the number of resource records a zone can own. In general, there can be zero, one, or more resource records of a given type. However, there are constraints on the number of certain types of records a zone can have.

All resource records have the following required entries:

Name—Name (host) that owns the record, such as example.com.

Class (not required for all formats)—DNS supports only the IN (Internet) class of record.

TTL (time to live)—Amount of time to store the record in cache, in seconds. If you do not include a TTL, Network Registrar uses the zone default TTL, defined in the SOA resource record.

Type—Type of the record, such as A, NS, SOA, and MX. There are many types that various RFCs define, although ten or fewer are in common use.

Record data—Data types whose format and meaning varies with record type.

Table A-1 lists all the resource record types Network Registrar supports. It provides the field syntax and the field descriptions, as well as how the fields are represented in the Network Registrar GUI.

Table A-1 Resource Records 

This record...
Data type...
Means...
The fields are...
As described in...

A

1

Host Address—
Name-to-
address mapping for the zone

owner class ttl A address

CLI entry example:

nrcmd> zone example.com addRR host123 3600 
       IN A 192.168.40.123 
100 Ok
host123 3600 IN A 192.168.40.123

GUI tab A: Name, TTL, Class, Type, Address

Name (owner)—Hostname expressed as an FQDN

Address (address)—32-bit IP address in dotted decimal form

There must be at least one A record for each host address.

RFC 1035

A6
(will replace AAAA records)

38

IPv6 Address—

owner class ttl A6 address

CLI entry example:

nrcmd> zone example.com addRR host456 A6 
       0 1345:c1:ca11:1:1234:5678:9abc:def0 
100 Ok
host456 IN A6 0 
1345:c1:ca11:1234:5678:9abc:def0

GUI tab Generic: Name, TTL, Class, Type, Data

Data (address) is in the format:

prefixlength suffixaddr prefixname

0 2345:00c1:ca11:0001:1234:5678:9abc:def0 

prefixlengthMust be 0 (the numbers 1 through 128 are currently not supported)

suffixaddr—IPv6 address (see below)

prefixname—Name of the prefix, encoded as a domain name

The suffix address is an IPv6 address encoded in network order (high-order octet first). There must be exactly enough octets in this field to contain a number of bits equal to 128 minus prefix length, with 0 to 7 leading pad bits to make this field an integral number of octets. Pad bits, if present, must be set to zero when loading a zone file and ignored on reception. For example:

2001:0:734c:c0:: 

RFC 2874

AAAA

28

SIPv6 Address—

owner class ttl AAAA address

CLI entry example:

nrcmd> zone example.com addRR host456 AAAA 
       1345:c1:ca11:1:1234:5678:9abc:def0" 
100 Ok
host456 IN AAAA 
1345:c1:ca11:1234:5678:9abc:def0

GUI tab Generic: Name, TTL, Class, Type, Data

Data (address)—IPv6 address format of eight sets of four hexadecimal digits, separated by colons. The first set of four digits is the high-order 16 bits of the address. You can omit leading zeroes in sets and omit a value in a set if the value of the set is zero.

RFC 1884

AFSDB

18

Andrew File System (AFS) Data Base—

owner class ttl AFSDB subtype hostname

CLI entry example:

nrcmd> zone example.com addRR host4 AFSDB 
       1 AFSDBhost.example.com. 
100 Ok
host456 IN AFSDB 1 AFSDBhost.example.com. 

GUI tab Generic: Name, TTL, Class, Type, Data

Data (subtype hostname)—

subtype

1—AFS cell database server

2—DCE authentication name server

hostname—Domain name of host that has a server for the cell named by the owner

RFC 1183

CNAME

5

Canonical Name—
Aliases or nicknames

owner class ttl CNAME canonicalname

CLI entry example:

nrcmd> zone example.com addRR host456 CNAME 
       host1234 
100 Ok
host456 IN CNAME host1234.example.com.

GUI tab CNAME: Name, TTL, Class, Type, Host

Name (owner)—Alias name

Host (canonicalname)—Canonical or primary host of the owner

You cannot have any other resource records associated with a CNAME. Aliases are useful when you want the outside world to know a single, easily remembered name. You can also use aliases when a host changes its name. In that case, make sure that you have a CNAME pointer so that when people use the original name, that it can be resolved to the newer one.

RFC 1035

HINFO

13

Host Info—
Hardware and software information for the host

owner class ttl HINFO cpu os

CLI entry example:

nrcmd> zone example.com addRR host5 HINFO 
       CPU1 OS2 
100 Ok
host5 IN HINFO "CPU1" "OS2"

GUI tab Generic: Name, TTL, Class, Type, Data

Data (cpu os)—

cpu—CPU type character string

os—Operating system type character string

RFC 1035

ISDN

20

Integrated Services Digital Network (ISDN) Address—

owner class ttl ISDN ISDNnumber [subaddr]

CLI entry example:

nrcmd> zone example.com addRR host6 ISDN 
       ISDN88888 
100 Ok
host6 IN ISDN "ISDN88888" ""

GUI tab Generic: Name, TTL, Class, Type, Data

Data (ISDNnumber subaddr)—

ISDN-number—ISDN number of the owner and Direct Dial In, if any

subaddr—Optional ISDN subaddress string

RFC 1183

MB

7

Mailbox Domain Name—

owner class ttl MB mbox

CLI entry example:

nrcmd> zone example.com addRR host7 MB 
       mailbox.example.com. 
100 Ok
host7 IN MB mailbox.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (mbox)Domain name of the host with the specified mailbox.

RFC 1035

MG

8

Mail Group Member—

owner class ttl MG mgroup

CLI entry example:

nrcmd> zone example.com addRR host7 MG 
       mbgroup.example.com. 
100 Ok
host7 IN MG mbgroup.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (mgroup)—Domain name of the mailbox group (mailing list).

RFC 1035

MINFO

14

Mailbox Info—

owner class ttl MINFO respmbox errormbox

CLI entry example:

nrcmd> zone example.com addRR host7 MINFO 
       resp.example.com. error.example.com. 
100 Ok
host7 IN MINFO resp.example.com. 
error.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (respmbox errormbox)—

respmbox—Mailbox responsible for the mailing list or mailbox for the owner mailbox

errormbox—Mailbox to receive error messages for the owner mailbox

RFC 1035

MR

9

Mail Rename—

owner class ttl MR newmbox

CLI entry example:

nrcmd> zone example.com addRR host7 MR 
       renamemb.example.com. 
100 Ok
host7 IN MR renamemb.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (newmbox)—Mailbox name to rename the owner mailbox

RFC 1035

MX

15

Mail Exchanger—
Where to deliver the mail for a domain name

owner class ttl MX pref mxname

CLI entry example:

nrcmd> zone example.com addRR host8 MX 10 
       exchanger.example.com. 
100 Ok
host8 IN MX 10 exchanger.example.com.

GUI tab MX: Name, TTL, Class, Type, Preference, Host

Name (owner)—Domain name of the host

Preference (pref)—16-bit integer for the preference for the record, with lower values having preference

Host (mxname)—Domain name of the mail exchanger for the owner

RFC 1035

NAPTR

35

Naming Authority Pointer—
Produces a new domain label or Universal Resource Identifier (URI). You can then use DNS to look up services for many resource names that are not in domain name syntax.

owner class ttl NAPTR order pref flags service regexp replace

CLI entry example:

nrcmd> zone 8.6.4.e164.arpa addRR 
       4.3.2.1.6.7.9 naptr 100 10 u sip+E2U 
       /^.*$/sip:info@tele2.se/ . 
100 Ok
4.3.2.1.6.7.8 IN NAPTR 100 10 "u" "sip+E2U" 
"/^.*$/sip:info@tele2.se/"
nrcmd> dns reload 

GUI tab Generic: Name, TTL, Class, Type, Data

Data (order pref flags service regexp replace)—

order—16-bit integer for the order in which to process the NAPTR records to ensure the correct ordering of rules, with low numbers processed before high numbers

pref—16-bit unsigned integer for the order in which to process NAPTR records with equal order values, with low numbers processed before high numbers

flags—Character-string containing flags to control aspects of rewriting and interpreting fields, single characters from the set [A-Z0-9] (case-insensitive); the S, A and U flags denote a terminal lookup, the P flag says that the remainder of the application-side algorithm should be carried out protocol-specific

service—Valid protocols or services

regexp—String containing a substitution expression applied to the original string held by the client to construct the next domain name to look up

replace—Next FQDN to query for NAPTR, SRV, or address records, depending on the value of the flags field

Note You must reload the server after adding this resource record.

RFC 2915

NS

2

Name Server—
Authoritative server for the zone

owner class ttl name NS nameserver

CLI entry example:

nrcmd> zone example.com addRR @ NS 
       DNSserv2.example.com. 
100 Ok
@ IN NS DNSserv2.example.com.

GUI tab NS: Name, TTL, Class, Type, Server

Name (name)—Domain of the host ("at" symbol, @, if the same as the owner)

Server (nameserver)—Domain name of host authoritative for the class and domain

Machines that provide name service must not reside in the owner domain. For each domain, you must have at least one NS record. NS records for a domain must exist in both the zone that delegates the domain and in the domain itself. NS record names must have an equivalent A record (they cannot point to an alias).

RFC 1035

NSAP

22

Network Service Access Point (NSAP) Address

owner class ttl NASP length NSAPaddr

CLI entry example:

nrcmd> zone example.com addRR host10 NSAP 
       4 23456789
100 Ok
host10 IN NSAP 4 23456789

GUI tab Generic: Name, TTL, Class, Type, Data

Data (length NSAPaddr)—

length—Number of octets in the NSAP address as defined by the various national and international authorities

NSAPaddr—Actual octet values assigned by the assigning authority, as a character string syntactically identical to that used in TXT and HINFO records.

RFC 1348

PTR

12

Pointer—
Reverse mapping

owner class ttl PTR dname

CLI entry example:

nrcmd> zone example.com addRR 
       45.40.168.192.in-addr.arpa. PTR 
       host1234 
100 Ok
45.40.168.192.in-addr.arpa. IN PTR 
host1234.example.com.

GUI tab PTR: Name, TTL, Class, Type, Data

Data (dname)—Domain name of host having the reverse record indicated by owner

Used for reverse mapping, specifically in the in-addr.arpa zones for translation of addresses to names. PTRs use official names, not aliases. The name in a PTR record is the local IP address portion of the reverse name.

RFC 1035

RP

17

Responsible Person—

owner class ttl RP mbox txthost

CLI entry example:

nrcmd> zone example.com addRR host7 RP 
       resp.example.com. text.example.com. 
100 Ok
host7 IN RP resp.example.com. 
text.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (mbox txthost)—

mbox—Domain name of the mailbox for the responsible person

txthost—Domain name of host where TXT records exist

RFC 1183

RT

21

Route Through—

owner class ttl RT pref intermediatehost

CLI entry example:

nrcmd> zone example.com addRR host7 RT 10 
       routthru.example.com. 
100 Ok
host7 IN RT 10 routthru.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (pref intermediatehost)—

pref—16-bit integer for preference to give to this record among others of the same owner

intermediatehost—Domain name of host serving as intermediate to reach the owner

RFC 1183

SOA

6

Start of Authority—
Every zone must have a single SOA record

owner class ttl SOA primeserver mbox (serial refresh retry expire minimum)

CLI entry example:

nrcmd> zone example.com addRR @ 172800 IN 
       SOA ns hostmaster 1 10800 3600 
       604800 86400 
100 Ok
@ IN SOA ns.example.com. 
hostmaster.example.com. 1 10800 3600 604800 
86400
nrcmd> dns reload 

GUI tab SOA: Name, TTL, Contact e-mail address, Name of primary server, Serial number, Secondary refresh time, Secondary retry time, Secondary expire time, Minimum TTL

Name (owner)—FQDN of the zone

TTL (ttl)—Default TTL for all the records in the zone, if not indicated in the record

Name of primary server (primeserver)—
Domain name of primary name server

Contact e-mail address (mbox)—Mailbox of the responsible person

Serial number (serial)—32-bit version number of the original copy of the zone

Secondary refresh time (refresh)—32-bit time interval before refreshing the zone

Secondary retry time (retry)—32-bit time interval before retrying a failed refresh

Secondary expire time (expire)—32-bit maximum time interval before declaring a zone no longer authoritative

Minimum TTL (minimum)—32-bit minimum TTL for all the records in the zone

Note You must reload the server after adding this resource record.

RFC 1035

SRV

33

Server—

owner class ttl SRV priority weight port target

CLI entry example:

nrcmd> zone example.com addRR host2 SRV 10 
       1 60 host7.example.com. 
100 Ok
host2 IN SRV 10 1 60 host7.example.com.

GUI tab Generic: Name, TTL, Class, Type, Data

Data (priority weight port target)—

priority—16-bit priority to give the record among the owner SRV records

weight—16-bit load to give the record at the same priority level

port—16-bit port on which to run the service

target—Domain name of host running on the specified port

Administrators can use several servers for a single domain, move services between hosts with little difficulty, and designate some hosts as primary servers for a service and others as backups. Clients ask for a specific service or protocol for a domain and receive the names of any available servers. See "Windows 2000 Interoperability," for how this record affects Windows 2000 servers.

RFC 2782

TXT

16

Text—

owner class ttl TXT textstrings

CLI entry example:

nrcmd> zone example.com addRR host2 TXT 
       this message 
100 Ok
host2 IN TXT "this message"

GUI tab Generic: Name, TTL, Class, Type, Data

Data (textstrings)—One or more text character strings less than or equal to 256 characters that can contain any type of information

RFC 1035

WKS

11

Well Known Services—

owner class ttl WKS addr protocol servicelist

CLI entry example:

nrcmd> zone example.com addRR host8 WKS 
       192.168.40.56 TCP TELNET 
100 Ok
host8 IN WKS 192.168.40.56 tcp telnet

GUI tab Generic: Name, TTL, Class, Type, Data

Data (addr protocol servicelist)—

addr—32-bit IP address

protocol—8-bit IP protocol number, which can be TCP or UDP

servicelist—Variable-length bit map in 8-bit multiples of services, which can be TIME, TELNET, FTP, or SMTP

RFC 1035

X25

19

X.25 Address—

owner class ttl X25 PSDNaddr

CLI entry example:

nrcmd> zone example.com addRR host9 IN X25 
       311061700956 
100 Ok
host9 IN X25 "311061700956"

GUI tab Generic: Name, TTL, Class, Type, Data

Data (PSDNaddr)—Character string of Public Switch Data Network (PSDN) address in X.121 numbering plan associated with the owner

RFC 1183