User Guide for Cisco Network Registrar 7.2
Appendix: Resource Records
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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 these 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, Cisco 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 Cisco Network Registrar supports. It provides the field syntax and the field descriptions, as well as how the fields are represented in the Cisco Network Registrar GUI.

Table A-1 Resource Records 

Record
No.
Name
Syntax and Description
RFC

A

1

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

name ttl class A address

Add or Edit Host for Zone page:  
Hostname, IP Address  
or Resource Records for Zone page:  
Name, TTL, Type, Data

1035

A6

38

IPv6 Address—
(Experimental; use AAAA records instead)

name ttl class A6 address

In the data, 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:: 

Resource Records for Zone page:
Name, TTL, Type=A6, Data=prefixlength suffixaddr prefixname, with data in the form:

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

2874

AAAA

28

IPv6 Address—

name ttl class AAAA address

Data is the 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 zeros in sets and omit a value in a set if the value of the set is zero.

Resource Records for Zone page: 
Name, TTL, Type=AAAA, Data=address 

1884

AFSDB

18

Andrew File
System (AFS)
Data Base—

name ttl class AFSDB subtype hostname

Subtype is either 1—AFS cell database server, or 2—DCE authentication name server. Hostname is the domain name of host that has a server for the cell named by the owner.

Resource Records for Zone page: 
Name, TTL, Type=AFSDB, Data=subtype hostname 

1183

CNAME

5

Canonical
Name—
Aliases or
nicknames

alias ttl class CNAME canonicalname

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, ensure that you have a CNAME pointer so that when people use the original name, it can be resolved to the newer one.

Resource Records for Zone page: 
Name=alias, TTL, Type=CNAME, Type, 
Data=canonicalname 

1035

DHCID

49

Dynamic Host Configuration Identifier— (RFC 4701)

name ttl class DHCID data

The DNS server uses this RR to allow DHCP clients and servers to update DNS automatically. This RR is not user-configurable. The data is the result of a one-way hash computation of the client message and the domain name. Sample RR output for an IPv6 address:

chi6.example.com IN DHCID 
( AAIBY2/AuCccgoJbaxcQc9TUapptP691OjxfNuVAA2kjEA= ) 

1035

HINFO

13

Host Info—
Hardware and
software
information
for the host

name ttl class HINFO cpu os

Data is the hardware (CPU) and operating system.

Resource Records for Zone page: 
Name, TTL, Type=HINFO, Data=cpu os

1035

ISDN

20

Integrated
Services Digital
Network (ISDN)
Address—

name ttl class ISDN ISDNnumber [subaddr]

Data is the ISDN number of the owner and Direct Dial In, if any, and an optional ISDN subaddress string

Resource Records for Zone page: 
Name, TTL, Type=ISDN, Data=ISDNnumber [subaddr]

1183

MB

7

Mailbox Domain
Name—

name ttl class MB mbox

Data is the domain name of the host with the specified mailbox.

Resource Records for Zone page: 
Name, TTL, Type=MB, Data=mbox

1035

MG

8

Mail Group
Member—

name ttl class MG mgroup

Data is the domain name of the mailbox group (mailing list).

Resource Records for Zone page: 
Name, TTL, Type=MG, Data=mgroup 

1035

MINFO

14

Mailbox Info—

name ttl class MINFO respmbox errormbox

Data is the mailbox responsible for the mailing list, and the mailbox to receive error messages.

Resource Records for Zone page: 
Name, TTL, Type=MINFO, Data=respmbox errormbox

1035

MR

9

Mail Rename—

name ttl class MR newmbox

Data is the mailbox name to rename the owner mailbox.

Resource Records for Zone page: 
Name, TTL, Type=MR, Data=newmbox 

1035

MX

15

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

name ttl class MX pref mxname

Data is the preference value (16-bit integer for the preference for the record, with lower values having preference), and the domain name of the mail exchanger for the owner.

Resource Records for Zone page: 
Name, TTL, Type=MX, Data=pref mxname

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.

name ttl class NAPTR order pref flags serv 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] (not case-sensitive); 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.

serv—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. (For common regex usage, see Table 5-4 on page 5-36).

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

Resource Records for Zone page: 
Name, State, TTL, Type=NAPTR, Data=order pref flags 
service regexp replace

2915

NS

2

Name Server—
Authoritative
server for the
zone

name ttl class NS nameserver

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).

Add or Edit Zone page Nameservers:  
NS TTL, Add Nameserver

1035

NSAP

22

Network Service
Access Point
(NSAP) Address—

name ttl class NASP NSAPaddr

Data is the NSAPaddr—Octet values assigned by the assigning authority, a character string of the type used in TXT and HINFO records (see RFC 1706).

Resource Records for Zone page: 
Name, TTL, Type=NSAP, Data=NSAPaddr

1706

PTR

12

Pointer—
Reverse
mapping

name ttl class PTR dname

Data is the domain name of host having the reverse record indicated by the owner. PTR records are 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.

Resource Records for Zone page: 
Name, State, TTL, Type=PTR, Data=dname 

1035

RP

17

Responsible
Person—

name ttl class RP mbox txthost

Data is the domain name of the mailbox for the responsible person, and the domain name of host where TXT records exist.

Resource Records for Zone page: 
Name, TTL, Type=RP, Data=mbox txthost 

1183

RT

21

Route
Through—

name ttl class RT pref intermediatehost

Data is the pref—16-bit integer for preference to give to this record among others of the same owner, and intermediatehost—domain name of the host serving as intermediate to reach the owner.

Resource Records for Zone page: 
Name, TTL, Type=RT, Data=pref intermediatehost 

1183

SOA

6

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

name ttl class SOA primeserver hostmaster (serial refresh retry expire minimum)

Add or Edit Zone page SOA Attributes:  
Serial Number, SOA TTL, Nameserver, Contact E-Mail, 
Secondary Refresh, Secondary Retry, Secondary Expire, 
Minimum TTL

1035

SRV

33

Service Location—

name ttl class SRV 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 Chapter 28, "Configuring DNS Update" for how this record affects Windows servers.

Resource Records for Zone page: 
Name, TTL, Type=SRV, Data=priority weight port target

2782

TXT

16

Text—

name ttl class TXT textstring

Data is one or more text character strings that can contain any type of information.

Resource Records for Zone page: 
Name, TTL, Type=TXT, Data=textstring 

1035

WKS

11

Well Known
Services—

name ttl class WKS 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.

Resource Records for Zone page: 
Name, TTL, Type=WKS, Data=addr protocol servicelist 

1035

X25

19

X.25 Address—

name ttl class X25 PSDNaddr

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

Resource Records for Zone page: 
Name, TTL, Type=X25, Data=PSDNaddr 

1183