DNS Records contains the data that will be returned to the client when the client requests information from the server about hosts or resources on the Network. There are lots of DNS records but we will look at the most common ones.
Start Of Authority (SOA) :
A start of authority (SOA) record is information stored in a domain name system (DNS) zone about that zone and about other DNS records. A DNS zone is the part of a domain for which an individual DNS server is responsible. Each zone contains a single SOA record. It is the DNS Server which has the most authority to make changes in the Domain.
It contains the following :
- Primary Name Server
- Email of Administrator
- Domain Serial Number : This tells other DNS Zones which version of DNS Zone that server contains. When changes are made to the Zone, the Serial Number will increase.
- Check the SOA records of any website here.
Host ( A & AAAA) :
- This Record maps the Domain Name to IP Address.
- A records are used for IPv4 addresses.
- AAAA (Quad A) record is used for IPv6.
- Check AAAA Records here.
Alias (CNAME / CANONICAL) :
To help with administration, DNS allows to create an Alias Record called a CNAME.
- CNAME points to A or AAAA (Quad A) Record.
- When you attempt to Resolve a CNAME record, the corresponding A or AAAA record is returned.
- You can also change the destination with CNAME is pointing to in case you use new server.
- It saves from lot of re-configuration headaches on your network when things get change.
- Check CNAME Records here.
SRV (Service) Records :
Originally DNS was designed only to resolve hostname to IP addresses, since then it has expanded to allow users to find resources and services on the network.
- A Service Record allows a client to locate services on the network using DNS.
- Service Records are used by Active Directory to allow a client to locate a Domain Controller, this is why DNS is so important in windows environment.
MX ( Mail Exchange ) Records :
- When you attempt to send an e-mail, the e-mail server will read the MX Records for that domain.
- Each MX Record has a priority / preference.
- The lower priority MX Records are tried first.
- If the e-mail server can’t connect to the server with lowest MX priority, it will try the next one.
- Check MX Records here.
Name Server (NS) Records :
Name Server Records are saved with your Domain Name Company.
- NS Records are used to set your Name Servers.
- NS Record will tell you where to find Name Servers for your Domain.
- Mainly there are two : Name Sever, Backup Name Server.
- NS Records -> Name Server -> DNS Records
- Name server holds DNS Records, it tells the Internet where to find your website/webapp.
Pointer (PTR) Records :
There are other DNS Records types but PTR Records are the main types.
- PTR stands for pointer record.
- It maps an IP address to a name.
- You must create Reverse Lookup Zone for PTR Records.
- Reverse Lookup Zone are used for troubleshooting tools such as TRACERT and NSLOOKUP.
In Old days, you had to update your DNS Records manually. With Windows server 2000 came the ability for clients to update their DNS dynamically. This is controlled by the service, DHCP client.
To force an update of a client DNS record :
- Open Command Prompt with ADMIN privileges.
- Type command “ipconfig /registerdns”.
Note : With Dynamic Updates, you can also configure it to use Secure updates. This stops a hacker inserting their own records in DNS Server and redirecting user to the Hacker’s Server. And to use Dynamic updates, the client must be a Windows computer and be in windows domain.
If you have any query regarding DNS Records, please leave your comment below in comment section.