Home » news »

Learn to perform a DNS backup and restore

 

Records are the core of DNS

A DNS server answers queries called DNS lookups from other computers on the network. Computers send a DNS query to the DNS server, which returns the relevant information requested or forwards the request to another DNS server that better answers the query. There are more than 90 DNS record types, but the list below shows the eight most common ones.

An A DNS record is the most common. The A is short for address. These A records resolve host names to IP addresses. This request type is known as a forward lookup.

My lab’s domain is called mk.lab and has a domain controller named DC01 with an IP address of 192.168.15.20. In DNS, there is an A record with this host information.

The DNS Manager console provides a graphical representation of DNS records. Notice on the left-hand side, we have the domain name mk.lab. The right panel shows the records in the mk.lab zone. You can see the entry for DC01, the record type and the IP address associated with DC01.

DNS A record
Example of an A record in the DNS Manager console.

To query this information using PowerShell, use the following command:

Resolve-DnsName DC01.mk.lab

Name                            Type   TTL    Section    IPAddress
—-                            —-   —    ——-    ———
dc01.mk.lab                     A      211538 Answer     192.168.15.20

The opposite of an A record is a pointer (PTR) record. The previous command is an example of a forward lookup: I provided the name, and DNS returned the IP address. PTR records work in reverse: I provide an IP address, and DNS returns the host name. This is called a reverse lookup.

PTR record example
A PTR record contains the mapping of an IP address to a domain name.

To look up PTR records with PowerShell, run the following command:

Resolve-DnsName 192.168.15.20 | ft AutoSize

Name                          Type   TTL      Section   NameHost
—-                          —-   —      ——-   ——–
20.15.168.192.in-addr.arpa.   PTR    210407   Answer    dc01
20.15.168.192.in-addr.arpa.   PTR    210407   Answer    dc01.mk.lab

The last record type I will cover is a canonical name (CNAME) record that is used to reference a host with an alias. A CNAME record points to an A record.

To understand how CNAME works, let’s say I have a server called AZBUILD01 in my domain. To reach the server with the name MyTestServer, you can create a CNAME record for MyTestServer that refers to the AZBUILD01 DNS record.

Example of a CNAME record
A CNAME record maps an alias to a domain name.

PowerShell can look up all types of DNS records. The following PowerShell command queries the MyTestServer alias and outputs the DNS information.  

Resolve-DnsName mytestserver.mk.lab Server dc01

Name                        Type   TTL   Section    NameHost
—-                        —-   —   ——-    ——–
mytestserver.mk.lab         CNAME  3600  Answer     AZBuild01.mk.lab

Name       : AZBuild01.mk.lab
QueryType  : A
TTL        : 1200
Section    : Answer
IP4Address : 192.168.15.25

 

Related Posts

  • No Related Posts