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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.
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|
|
|
|
---|---|---|---|---|
A |
1 |
Host Address— |
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— |
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: 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 |
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 |
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— |
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 |
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 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 |
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 |
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 |
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— |
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 |
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— |
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 |
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 |
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 |
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 |
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 |