As a senior professional, you should aware list of DNS records and its purpose.
So, that you can understand exactly, why? these many records are combined with DNS.
What is DNS? DNS stand for Domain name System or Domain Name Server, which maps IP addresses to fully qualified domain names (FQDN) and vice versa.
1) List of records in DNS ?
DNS contain A, AAA, NS, MX, PTR, CNAME, SOA, TXT, SPF, DKIM
# host -a 2daygeek.com 2daygeek.com. 86321 IN SOA ns1.2daygeek.in. magesh.maruthamuthu.gmail.com. 2013110202 86400 7200 3600000 86400 2daygeek.com. 14233 IN TXT "v=spf1 ip4:22.214.171.124 +a +mx +ip4:126.96.36.199 ?all" 2daygeek.com. 12127 IN MX 0 2daygeek.com. 2daygeek.com. 12127 IN A 188.8.131.52 2daygeek.com. 12127 IN AAA 2400:cb00:2049:1::adf5:3bf5 2daygeek.com. 84127 IN NS ns1.2daygeek.in. 2daygeek.com. 84127 IN NS ns2.2daygeek.in. PTR 184.108.40.206.in-addr.arpa domain name pointer NSG-Static-070.233.71.182.airtel.in. CNAME www.2daygeek.com is an alias for 2daygeek.com. DKIM k=rsa; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC7Wn42bi7muo6PYvR+gBIngY1I..
Note : The above command will give the output upto NS records and remaining (PTR, CNAME & DKIM) i added manually for reference purpose. Use host or dig or nslookup command to check the DNS records in Linux.
2) A Record
A record stands for Address record. The
A record specifies the IP address (IPv4) of a host.
Whenever DNS server get a query to resolve domain-name, it will refer the A record to answer the IP address.
3) AAA Record
The ‘AAA’ record specifies the IP address (IPv6) of a host.
4) NS Record
NS Record stands for Name Server record. NS Records maps a domain name to a list of authoritative DNS servers.
5) MX Record
MX Record stands for mail exchange record. MX Records maps a domain name to a list of mail exchange servers.
6) PTR Record
PTR record stands for Reverse lookup record or Pointer record. A PTR record maps the IP address to a specific host.
7) CNAME Record
CNAME Record stands for Canonical Name. CNAME record is used to create aliases that point to other names such as WWW, FTP, MAIL & subdomains to a domain name.
Example : a CNAME record can associate the subdomain www.2daygeek.com with 2daygeek.com
8) SOA Record
SOA record stands for Start of Authority records. SOA records contain information about a DNS zone such as Primary nameserver, Hostmaster E-mail address, zone file seriel number, zone transfer interval and zone expiry details.
9) TXT Record
TXT Record stands for text record. A TXT record is a type of DNS record that provides text information to sources outside your domain. The text can be either human-or machine-readable and can be used for a variety of purposes.
10) SPF Record
SPF Record stands for Sender Policy Framework. SPF is an extension to the SMTP mail protocol which is used for e-mail authentication. SPF record used to verifies that the message came from an authorized mail server or not. SPF is designed to detect SPAM & PHISHING mail sender’s, IP address which was included in e-mail header.
11) DKIM Record
DKIM record stands for Domain Keys Identified Mail. DKIM is an email validation system designed to detect email spoofing by providing encryption authentication to receiving mail exchangers.
It will check whether the incoming mail domain is authorized by the domain’s administrators and that the email (including attachments) has not been modified during transport.
A digital signature included with the message can be validated by the recipient using the signer’s public key published in the DNS.