DNS Records Explained

Summary

In this video, the presenter explains DNS records, starting with how DNS works and its role in resolving domain names to IP addresses. The video covers key DNS records, including A records (IPv4), Quad A (IPv6), CNAME (aliases), MX (email routing), SOA (administrative info), NS (name servers), SRV (service-specific), PTR (reverse DNS), and TXT (miscellaneous and email authentication). The presenter also highlights how DNS zones are structured for manageability. Additionally, there is a brief promotion for Aura's security service, emphasizing privacy and data protection features.

Takeaways

• 🌐 DNS stands for Domain Name System and its primary function is to resolve domain names to IP addresses.
• 🔍 DNS hierarchy consists of root servers, top-level domain servers, and authoritative name servers, with authoritative name servers storing DNS records.
• 🏢 The process of resolving a domain name to an IP address involves queries passing through root and top-level domain servers before reaching the authoritative name server.
• 📄 DNS zone files contain DNS records, which are crucial for the functioning of the DNS system.
• 📑 The A record is the most common DNS record, resolving domain names to IPv4 addresses.
• 🕒 TTL (Time to Live) indicates how long a DNS record is valid before it needs to be refreshed.
• 🌐 The AAAA record is similar to the A record but resolves domain names to IPv6 addresses.
• 🔗 CNAME (Canonical Name) records create aliases for domain names, allowing one domain or subdomain to point to another.
• 💌 MX (Mail Exchange) records direct emails to the appropriate email server for a domain.
• 🛠 SOA (Start of Authority) records store administrative information about a DNS zone, including the primary name server and the administrator's contact information.
• 🌐 NS (Name Server) records identify the authoritative name servers for a domain.
• 📞 SRV (Service) records locate specific services on a domain, including the server and port number.
• 🔄 PTR (Pointer) records perform reverse DNS lookups, resolving IP addresses back to domain names, which is useful for email authentication.
• 📝 TXT (Text) records contain miscellaneous information about a domain, and can be used for email spam prevention and other notes.

Q & A

What is the primary function of DNS?

The primary function of DNS is to resolve domain names to IP addresses, as computers understand numbers rather than names.

What are the three main levels of servers in the DNS hierarchy?

The three main levels of servers in the DNS hierarchy are root servers, top-level domain servers, and authoritative name servers.

What is the role of authoritative name servers in DNS?

Authoritative name servers are responsible for storing DNS records that resolve domain names to IP addresses and are the final authority in the DNS hierarchy.

How does a DNS query resolve a domain name to an IP address?

A DNS query first goes through the root server, then to the top-level domain server, and finally to the authoritative name server responsible for the domain, which resolves the domain name to an IP address.

What is a DNS zone file and what does it contain?

A DNS zone file is a file in a DNS database that contains DNS records, which are essential for resolving domain names to IP addresses and other related information.

What is an A record in DNS and what does it resolve to?

An A record, or address record, is the most common DNS record that resolves a domain name to an IPv4 address, which is a 32-bit numeric address.

What is the difference between an A record and a AAAA record?

An A record resolves domain names to IPv4 addresses, while a AAAA record resolves domain names to IPv6 addresses, which are 128-bit alphanumeric addresses.

Can you explain the purpose of a CNAME record?

A CNAME record, or canonical name record, resolves a domain or subdomain to another domain name, essentially acting as an alias for another domain name.

What is an MX record and how is it used for email?

An MX record, or mail exchanger record, is used for directing emails to the correct server for a domain name. It points to the server where emails should be delivered.

What administrative information does an SOA record store?

An SOA record, or start of authority record, stores administrative information about a DNS zone, including the primary name server, the administrator's email address, and the zone's version number.

What is the purpose of an NS record in DNS?

An NS record, or name server record, provides the name of the authoritative name server within a domain, indicating the final authority for DNS queries within that domain.

How does an SRV record differ from other DNS records?

An SRV record, or service record, points to a server and also specifies a service by including a port number, unlike other records that typically point to a server or IP address.

What is the purpose of a PTR record in DNS?

A PTR record, or pointer record, resolves IP addresses to domain names, which is the reverse of what A or AAAA records do. It is used to verify the authenticity of email senders to prevent spam.

What type of information can be stored in a TXT record?

A TXT record contains miscellaneous information about a domain, such as general or contact information, and can also be used to prevent email spam by verifying the source of incoming emails.

Outlines

00:00

🌐 DNS Records Explained

This paragraph introduces DNS records, explaining their function within the domain name system (DNS) to resolve domain names to IP addresses. It reviews the DNS hierarchy, highlighting the role of root servers, top-level domain servers, and authoritative name servers. The focus is on authoritative name servers, which store DNS records. The process of resolving a domain name to an IP address is detailed, starting from the root server and moving through top-level domain servers to the authoritative name server responsible for the domain. The paragraph also mentions DNS zone files, which contain DNS records, and introduces the most common types of DNS records.

05:01

🔍 Common DNS Records

The paragraph delves into the specifics of common DNS records. It starts with the A record, which maps domain names to IPv4 addresses, and mentions the TTL field that dictates the validity period of records. The AAAA record is introduced as the IPv6 equivalent of the A record. The CNAME record is explained as an alias for another domain name, useful for subdomains sharing the same IP address, such as www.example.com. The MX record is discussed for its role in directing emails to the correct mail server based on priority. The SOA record is described as containing administrative information about a DNS zone, which can be delegated to different administrators for manageability. The paragraph also touches on the importance of DNS zones for dividing a domain namespace and the role of SOA records within them.

10:03

📝 Additional DNS Records and Their Functions

This paragraph continues the discussion on DNS records, describing the NS record that identifies the authoritative name server for a domain. The SRV record is introduced for directing applications to specific services on a server, including port numbers. The PTR record is explained as the reverse of A or AAAA records, resolving IP addresses back to domain names, which is crucial for email authentication and spam prevention. The TXT record is mentioned for storing miscellaneous information about a domain, which can also be used for email spam prevention and other purposes. The paragraph concludes with a call to action for viewers to subscribe and a reminder about Aura's two-week free trial, emphasizing internet safety tools provided by Aura.

Keywords

💡DNS

DNS stands for Domain Name System, which is a system that translates human-friendly domain names (like 'example.com') into IP addresses that computers use to identify each other on the internet. It's fundamental to the functioning of the internet, as it allows users to access websites without needing to remember numerical IP addresses. In the video, DNS is explained as resolving domain names to IP addresses, which is its most basic job.

💡Domain Name

A domain name is the address where Internet users can access your website. A domain name is used in various formats (example.com, blog.example.com, etc.) and is an easy-to-remember address which can be typed into the address bar of a web browser to access a website. In the script, domain names are used to illustrate how DNS resolves them into IP addresses.

💡IP Address

An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. Computers communicate over a network by sending information to each other's IP addresses. The video script uses IP addresses to explain how DNS maps domain names to the numerical addresses that computers understand.

💡Root Server

The root server is the highest level of the DNS hierarchy and is responsible for managing the overall domain namespace. It directs DNS queries to the appropriate Top-Level Domain (TLD) servers. In the video, the script describes how a query for 'example.com' would first go to the root server before being directed to the .com TLD server.

💡Top-Level Domain (TLD) Server

A TLD server is responsible for the information of top-level domains such as .com, .net, .org, etc. It is the second level in the DNS hierarchy. The script mentions that after the root server, the query is forwarded to the appropriate TLD server based on the domain's suffix (e.g., .com for 'example.com').

💡Authoritative Name Server

Authoritative Name Servers are the servers that have the actual DNS records for a domain. They are responsible for knowing everything about the domain, including its IP addresses. The video script explains that these servers are crucial for resolving domain names into IP addresses.

💡DNS Zone File

A DNS zone file is a database that contains the DNS records for a particular domain. It is used by the DNS server to respond to DNS queries. The script mentions DNS zone files as the place where DNS records are stored within a DNS server.

💡A Record

An A record, or address record, is a type of DNS record that maps a domain name to its IPv4 address. The video script uses the A record as an example of how DNS uses this record to resolve a domain name to an IP address.

💡CNAME Record

A CNAME record, or canonical name record, is a type of DNS record that specifies one domain name as an alias for another. It is used to map a subdomain to a primary domain. The script gives an example of creating a CNAME record for 'www.example.com' that points to 'example.com'.

💡MX Record

An MX record, or mail exchange record, is a type of DNS record that specifies the mail server responsible for accepting email messages on behalf of a domain. The video script explains how MX records are used to direct emails to the correct server for a domain.

💡SOA Record

An SOA record, or start of authority record, is a type of DNS record that defines the administrator of a DNS zone and the technical details of the zone. The script describes the SOA record as storing administrative information about a DNS zone.

💡NS Record

An NS record, or name server record, is a type of DNS record that specifies which DNS servers are authoritative for a domain. The video script mentions NS records as providing the names of the authoritative name servers within a domain.

💡PTR Record

A PTR record, or pointer record, is a type of DNS record that performs the opposite function of the A record. It maps an IP address to a domain name, allowing reverse DNS lookups. The script explains how PTR records are used to prevent email spam by verifying the authenticity of the sender's domain.

💡TXT Record

A TXT record is a type of DNS record that can contain descriptive text about a domain. It's often used for email verification and to provide additional information about a domain. The script mentions TXT records as containing miscellaneous information about a domain.

Highlights

DNS is essential for resolving domain names to IP addresses, which computers understand.

There are three main levels of DNS servers: root, top-level domain, and authoritative name servers.

Authoritative name servers store DNS records for domain name resolution.

DNS queries must pass through the root server before reaching the authoritative name server.

DNS zone files contain DNS records, which are crucial for domain name resolution.

A record (address record) is the most common DNS record, resolving domain names to IPv4 addresses.

TTL (time to live) indicates how long a DNS record is valid before needing an update.

AAAA (quad A) records are similar to A records but resolve domain names to IPv6 addresses.

CNAME (canonical name) records create aliases for domain names, useful for subdomains.

MX (mail exchanger) records direct emails to the correct server for a domain.

SOA (start of authority) records store administrative information about a DNS zone.

DNS zones allow a domain to be divided into sections, each with its own administrator.

NS (name server) records provide the names of authoritative name servers within a domain.

SRV (service) records point to a server and a specific service, including a port number.

PTR (pointer) records resolve IP addresses to domain names, used for reverse DNS lookups.

TXT (text) records contain miscellaneous information about a domain, used for email spam prevention.

Aura is a service that identifies data brokers exposing personal information and helps opt-out.

Aura offers an app with antivirus, password manager, and real-time credit and identity theft monitoring.

Aura's VPN provides fast and secure internet browsing.

Aura's two-week free trial allows users to see how much personal information is exposed.

Transcripts

Hello everyone in this video we're going to  be talking about DNS records. Now if you saw my  

original DNS video, I talked about how DNS works.  But in this video we're going to talk about the  

specifics of DNS records that you would find in a  DNS server's database. So as a refresher, DNS stands  

for domain name system. And the most basic job of  DNS is to resolve domain names to IP addresses.  

And the reason it has to do this is because computers don't understand names, they only understand  numbers.

A domain name is just a text that you  type in a web browser when you want to go to  

a certain website such as example.com, google.com,  yahoo.com, and so on. So when you type in a domain  

name such as example.com in a web browser, DNS will resolve that domain name into an IP address so you  

can retrieve the website. Now in a DNS hierarchy  there are three main levels of servers. There are  

the root servers, the top level domain servers,  and the authoritative name servers. But of these  

three the DNS servers that are responsible for  storing the DNS records for resolving domain  

names to IP addresses are the authoritative name  servers because they are responsible for knowing  

everything about the domain name, including  the IP addresses and much more. But in order  

for your query to resolve example.com into an IP  address, it needs to know which name server to ask  

So in order to find the correct name server,  the query must first go through the top of  

the DNS hierarchy which is the root server. And  once it reaches the root server, the root server  

will look at example.com and will forward the  query to the correct top level domain server. The  

top level domain server is responsible for  information of top level domains, such as  

.com .net .org and so on. So in this case the  root server will forward the query to the .com  

top level domain server because the top level  domain for example.com is .com. And then the top  

level domain server will forward the query to  the specific authoritative name server that's  

responsible for the example.com domain. And once  the query reaches the name server, example.com will  

be resolved to the IP address so the website can  be retrieved. So in a DNS database you have what's  

called a DNS zone file and this file contains the  DNS records. Now there are numerous DNS records  

but I'm only going to talk about the most common  ones. Hey guys I just want to break in this video  

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So the first DNS record is the A record or address  record. And this is the most common DNS record 

This is what resolves a domain name to an IP address. To be specific it resolves to an IPv4 address which  

is a 32-bit numeric address. So in the example  we just did earlier, when you type in a domain  

name such as example.com in a web browser, the  A record is what DNS uses to resolve a domain  

name to an IP address. And then we also have  the TTL or time to live, this field tells us  

how long each record is valid until the next  update. And then there's also the quad A record  

And this record is just like the A record. So  both A and quad A records resolve domain names  

to IP addresses, but the difference is, is that  quad A records resolve domain names to IPv6  

addresses. An IPv6 address is 128-bit alphanumeric  address that's replacing the older IPv4 addresses  

The next DNS record is called CNAME or canonical  name. And what this does is that it resolves a  

domain or subdomain to another domain name. So  basically it's an alias for another domain name  

So as an example, computers read domain names from right to left and domain names will have several  

parts: a root domain, a top level domain, a second  level domain, and a subdomain. So when we look at  

example.com there is also a hidden dot right after  com even though it's hidden and we don't see it  

but that dot is the root domain. The .com is the  top level domain and example is the second level  

domain. But if there is an additional name to the  left of a second level domain then that would be a  

subdomain. So for example www is a common subdomain, which is why it is common to create a CNAME record  

pointing www.example.com to example.com. Which is why when you type example.com or www.example.com  

in your web browser you'll end up at the same  example.com website because of that CNAME record  

Subdomains are also often used when a website has  different services running on the same server and  

are using the same IP address. So as an example  let's say that example.com has an FTP service  

running on the same server as their website.   So in this case they can create a subdomain  

such as ftp.example.com for their FTP service  on the server and then they can create a CNAME  

record and have it directed to example.com. So now when users type in ftp.example.com  

in their web browser, DNS will look at the CNAME record and forward the users to example.com. Now even  

though it's pointing to example.com but once  the request reaches the web server, the web  

server will inspect the URL that the user  has typed and direct it to its FTP service  

on the server. So CNAME records are similar to A records but the difference is, is that A records  

resolve domain names to IP addresses while  CNAMES resolve domain names to domain names  

And the next DNS record is MX record or mail  exchanger record. And this record is used for  

email. The MX record simply points to the server  where emails should be delivered for that domain  

name. So for example when you send an email to [email protected], your MTA or mail transfer agent will  

query the MX records for example.com because  it's looking for an email server. And then DNS  

will respond back telling the MTA which server  to send the email to which in this case would  

be mail1.example.com because that's what the MX  record points to. So that's basically what the  

MX record does, it tells the world which server  to send email to for a particular domain name  

Now MX records will generally have  two entries, a primary email server  

and a secondary email server along with  priority numbers. The lower the priority  

number means that it's the primary email  server. But if the primary email server  

gets overwhelmed or goes down, then the  secondary email server would be used

And the next DNS record is called SOA which stands  for start of authority. And what this does is that  

it stores administrative information about a DNS  zone. So what are DNS zones? Well a DNS zone is a  

section of a domain name space that a certain  administrator has been delegated control over. 

DNS zones allow a domain namespace such as example.com to be divided into different sections. So if we  

look at the domain example.com, if this domain was  broken down into three sections or subdomains such  

as shop.example.com, blog.example.com, and  support.example.com, the head administrator  

could create DNS zones and delegate control over  these subdomains to different administrators if  

he chooses to. So let's say that the shop and  blog subdomains have only a few computers in  

each domain and the support subdomain has many  computers. So since these two only have a small  

amount of computers, the head admin could create  one zone for these two subdomains and assign  

an administrator to manage it. But since support  has so many computers, the head administrator has  

created another separate zone just for the support  subdomain and then he or she will assign another  

administrator to manage it. So DNS zones are  created for manageability purposes and each will  

have their own DNS zone file which contains an  SOA record. So here is an example of an SOA record  

So just to go over a few of these categories. The  MNAME is the primary name server. The RNAME is the  

email address of the administrator for this zone,  where this dot here represents the @ symbol in  

an email. And the serial number is a number that  represents a version in the zone. So whenever an  

update happens in the zone, the serial number  will change which tells the secondary servers  

to update as well. And the next record is the  NS record which stands for name server. Now  

this record, just like its name says, provides the  name of the authoritative name server within a  

domain. So as I stated previously, the name server  contains all the DNS records necessary for users  

to find a computer or server on a local network  or on the Internet. It is a final authority in a  

DNS hierarchy. And an NS record would generally  list two name servers: a primary and a secondary  

And the next DNS record is called SRV which  stands for service record. Now the previous  

DNS records that we talked about will point to  a server or an IP address. But a service record  

will point to a server and it'll also point to  a specific service by including a port number. So  

when an application needs to find the location  of a service on a domain such as voice over IP,  

instant messaging, or a printer, it will look for  a service record to see if there's a listing for  

that specific service and it will direct it  to the correct server and correct port number

And then we have a PTR or pointer record. Now this  record is basically the reverse of an A or a quad  

A record. So as you remember, A and quad A records  resolve domain names to IP addresses but PTR  

records do the opposite, they resolve IP addresses  to domain names. PTR records are attached to email  

and are used to prevent email spam. So whenever an  email is received, the email server uses the PTR  

record to make sure that the sender is authentic  by matching the domain name in the email with its  

authentic IP address. This is what's known as a  reverse DNS lookup. But if an email that is sent  

does not match with its correct and authentic  IP address, the email will be flagged as spam

And our last record is the TXT or text. Now this record contains miscellaneous  

information about a domain such as general  or contact information. These are also used  

to prevent email spam by making sure  incoming email is coming from a trusted  

or authorized source. They can also contain  other miscellaneous texts such as be sure  

you sign up for Aura's two-week free trial  at aura.com/powercert. So guys I  

want to thank you for watching this video. Please  subscribe and I will see you in the next video