DNS Records – Part 2

Aug 19 2017- POSTED BY projecth 0 Comment

TXT Records

These records can contain freeform text of any type.
They are generally used by service providers as well as email services to verify domain ownership.

A TXT record can contain the following to prove ownership:
google-site-verification=asknsdUDP123lkmansdonid12e09djda09u1e

 

SPF Records

Sender Policy Framework.
SPF tells you what kind of hosts can send and receive mail on your behalf. This help to reduce SPAM.
When you’re creating an SPF record, it deals with different mechanisms:

  • + means the record will pass.
  • - means it will fail.
  • ~ means there will be a soft failure.
  • ? neutral.

Example
v=spf1 include:_spf.google.com ~all
This means that spf.google.com will manage sending emails on your behalf.

This type of thing can be very useful when you’re looking for email delivery.
Spam has become a big problem, so things like SPF and DKIM have been invented.

DomainKeys Identified Mail (DKIM)

It is a method for associating a domain name with an email message, thereby allowing a person, role, or organization to claim some responsibility for the message.

 

Pointer Records (PTR)

PTR records are used for something called “Reverse DNS”.
They are mainly used to check if the server name is actually associated with the IP address where connection was initiated from.

PTR records also determine that a domain name is associated with a given IP. It’s kind of opposite to the way an A record works.
Useful for Forward-confirmed reverse DNS, which will ensure that both the PTR and A records match.

Example
mail.teamtreehouse.com PTR and A records both go to the same IP address.

PTR Record Format

ReversedIPAddress.in-addr.arpa

Example
mail.teamtreehouse.com points to 1.2.3.4
The PTR record is:

4.3.2.1.in-addr.arpa

 

SOA Records

The Start of Authority is the first entry in the DNS zone file.
The SOA indicates that this DNS name server is the best source for data within this domain.

Start of Authority Information and Format
  • Source host
  • Contact email using a dot (admin.example.com)
  • Serial Number
  • Refresh time in seconds
  • Retry Time
  • Expire Time
  • Minimum TTL