DNS Records Explained
Summary
TLDRIn 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
🌐 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.
🔍 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.
📝 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.
Mindmap
Keywords
💡DNS
💡Domain Name
💡IP Address
💡Root Server
💡Top-Level Domain (TLD) Server
💡Authoritative Name Server
💡DNS Zone File
💡A Record
💡CNAME Record
💡MX Record
💡SOA Record
💡NS Record
💡PTR Record
💡TXT Record
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
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