| Lesson 3 | Finding other record types |
| Objective | Use nslookup to read other Types of Resource Records. |
Use nslookup to read other Types of Resource Records
In its simplest form,
nslookup extracts the A and PTR records from the DNS database. However, it is sometimes interesting (or useful) to use the nslookup command to read the SOA,
HINFO, and other record types as well. To ask nslookup to extract other kinds of records, use the set type command.
- Address (A) record: An A record is a type of Resource Record that specifies an IP address-to-host name mapping.
- Pointer (PTR) record: A PTR record is a type of Resource Record that specifies a host name-to-IP address mapping.
- State of Authority (SOA) record: An SOA record is a type of Resource Record that sets basic parameters for a DNS zone of authority and marks the beginning of a zone. Every zone or subzone must have exactly one SOA record and the zone continues until another SOA record is encountered.
- Host information (HINFO) record: An HINFO record is a type of Resource Record that gives the operating system and architecture for the specified host.
- The set type command requests nslookup to obtain the full SOA Resource Record
- The set type command requests nslookup to obtain the full SOA Resource Record.
- The authoritative server for the acmetraining.com organization is ns1.portal.ca.acmetraining.com, and the responsible party is hostmaster.portal.ca.
- In this example, nslookup has also extracted NS records.
- In this example, nslookup has also extracted A records for the name servers.
Set type Command Output
nslookup Query
Examine the output of this command. This information came in a single
nslookup query. In addition to the answer to a particular question, DNS queries contain authority information explaining where the information came from, and additional information
which may be helpful. In our example, the authority information is the name server records, and the additional information is their IP addresses.
This information saves you from having to do an additional A record query.
View Example: an HINFO query using nslookup
View the example below, this time with an HINFO query.
Note the HINFO record describing the machine raphael.math.uic.edu, together with the authority records and additional information.
System Information Record (HINFO): This record allows definition of the Hardware type and Operating System (OS) in use at a host. For security reasons these records are rarely used on public servers. If a space exists in the field it must be enclosed in quotes.
System Information Record (HINFO): This record allows definition of the Hardware type and Operating System (OS) in use at a host. For security reasons these records are rarely used on public servers. If a space exists in the field it must be enclosed in quotes.
$ nslookup Default Server: dns.class.com Address: 196.241.12.122 > set type=HINFO > raphael.math.uic.edu Server: dns.class.com Address: 196.241.12.122 raphael.math.uic.edu CPU = Intel OS = linux math.uic.edu nameserver = newton.math.uic.edu math.uic.edu nameserver = dns2.math.uic.edu math.uic.edu nameserver = uic-dns1.uic.edu math.uic.edu nameserver = uic-dns2.uic.edu math.uic.edu nameserver = uic-dns3.uic.edu newton.math.uic.edu internet address = 131.193.178.229 uic-dns1.uic.edu internet address = 128.248.2.50 uic-dns2.uic.edu internet address = 128.248.7.50 uic-dns3.uic.edu internet address = 128.248.171.50