DNS Records
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- เผยแพร่เมื่อ 15 พ.ค. 2024
- In order to find resources on the network, computers need a system to look up the location of resources. Check out / itfreetraining or itfreetraining.com for more of our always free training videos. This video looks at the DNS records that contain information about resources and services on the network. The client can request these records from a DNS server in order to locate resources like web sites, Active Directory Domains and Mail Servers just to name a few.
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In this video
This video will look at the following DNS records:
Host (A and AAAA): Contains IP Addresses for IPv4 and IPv6 hosts
Alias (CNAME): Works just like a shortcut for files except for DNS records.
Mail Exchange (MX): Holds the address of mail servers for that domain.
Service Record (SRV): Holds the address of services on the network. E.g. Active Directory DC's.
Start of Authority (SOA): Contains information and configuration for a zone file.
Name Server (NS): Contain the address of other DNS servers for that zone.
Pointer (PTR): Reverse look up record allowing a hostname for an IP Address to be look up.
Host (A and AAAA)
The host record is used to store the address of a hostname. "A" is used for IPv4 and AAAA (Quad A) for IPv6. These can be created manually in DNS or if dynamic DNS is enabled and the client can register its hostname and thus its IP Address with the DNS server.
Alias (CName)
A canonical name or CName record provides an alias service in DNS. A CName effectively points to another A or Quad A record. When the client requests the hostname that is contained in the CName, they are given the IP Address that is contained in the A record or Quad A record. The advantage of a CName is that it can provide a simple name to the user rather than a more complex server name. For example, instead of having to remember FS27 for the local file server, a CName of FS could be used to point towards the server FS27. CName's can also be used to transparently redirect network traffic. For example, if you changed you mind and wanted to redirect the user to FS28 you would only need to change the CName record to point to FS28 rather than FS27. It should be remembered that the old record may exist in the client cache and may take some time to expire.
Mail Exchange (MX)
The mail exchange record contains a mail server that is able to process mail for that domain name. When a mail server wants to deliver mail, it will perform a DNS lookup asking the DNS server for an MX record for that DNS Domain name. The mail server will then attempt to deliver mail to that server. The mail server does not need to have the same DNS name as the mail that is being delivered, it simply needs to understand how to process mail for that DNS domain name.
The MX record also has priority value that can be configured. If two or more MX Exchange records exist for the same DNS Doman name, the MX record with the lowest priority will be tried first. If this fails, the MX record with the next lowest value will be tried until the mail is delivered. Often large companies will have multiple mail severs for incoming mail. In some cases, these additional mail servers may be located on different sides of the globe in case there is a long network outage.
Service Record (SRV)
Service records allow clients on the network to find resources on the network. Active Directory creates a number of service records in DNS to allow clients to find resources like Domain Controllers. This is why Active Directory cannot operate without DNS. A single service record has a number of data fields associated with it. These include, service, target, port and priority. Service records are normally created automatically by applications assuming that your DNS server allows dynamic updates.
Start of Authority (SOA)
There is one start of authority record (SOA) for each zone. Even though the SOA is technically a DNS record, essentially modification of the SOA record is performed through the properties of the DNS zone. Looking at the data in the SOA record, you can configure options for the zone like the primary name server for that zone (DNS servers that hold the master records for the zone), the e-mail address of an administrator, serial number (Incremented each time a change is made in the DNS zone) and the refresh time for the zone (How often a secondary zone should query a master for changes).
Video description to long for TH-cam. For full description please see itfreetraining.com/70-642/dns-...
See / itfreetraining or itfreetraining.com for our always free training videos. This is only one video from the many free courses available on TH-cam.
References
"MCTS 70-640 Configuring Windows Server 2008 Active Directory Second edition" pg 458 -- 459
"Installing and Configuring Windows Server 2012 Exam Ref 70-410" pg 236-237
"SRV record" en.wikipedia.org/wiki/SRV_record
Thanks, glad to hear that you like the videos.
No problem at all. Thanks for watching.
Thank you for the clear and concise lesson! So helpful!
Its just due to your videos i am able to understand windows servers. May God bless you guys.
Farukh Shaikh Thanks very much, glad we could help you
Thanks Sir! I have been looking for somthing that can help me with my mail server but finally! I didnt know that i was using the wrong record...
Good presentation - clearly miked and clearly delivered, good plain English explanations. I feel as if
I understand SOA and NS records much better now. Thanks!
You're most welcome! Thank you for your kind feedback. :)
Thanks Adam! Good Luck taking them
This is a good and very well presented video and I'm very grateful for You making and sharing it.
That said I think it could have been even better if it had used more "graphical slides", if the type You used when explaining (clarifying) the "MX record". Showing an "over view" of where (in the network) the different records would be "held".And how they would "querried and answer" to fulfill their function is something I believe would facilitate learning and grasping the context of, and relation between the different records.
Again many thanks for making and sharing this excellent content
Best regards.
I am so glad that you made available this information and video.* Also the narration and manner used.
Thanks very much. Glad to hear that you like the video.
You have a collection of great videos. Very informative!
Thanks for the great feedback! We appreciate you choosing ITFreeTraining!
Thanks guys this is brilliant your going to help me get me through my exams for 70-410 :-)
Much appreciated the graphics and explanation. Keep up the amazing work!
Much appreciated!
i still watch ur awesome expalnations, and it is jus so good.
You are truly amazing. THANK YOU.
You're welcome! Thanks for the amazing feedback. :)
very good ,this lesson explain the knowledge very well. thanks
Thanks very much. Glad we could help.
Very clear explanations. Keep up the good work !
thx
Thanks very much. More videos to come.
I love your presentations.
Excellent right to the point explanations. Thanks a lot!
Glad it was helpful!
Thank you for this explanation. I understood it much better than Google IT Training's explanation.
You are welcome!
Thank you.
You got the art of explaining, you are the best
Yeah, he is best by FAR. The others tend to fall into the trap of starting off by using too many SIMPLE analogies and then when the topic goes deeper, it gets harder for them to find perfectly equivalent concepts in the analogy, to keep using that analogy in a manner that is STILL relevant/meaningful to the topic 😁
@@TebogoMotlhale exactly, some times calling things by their real names works much better then exaustive analogies
Thanks very much.
Very clear explanations. Keep up the good work !
Thanks for watching.
Great job.. a value added would have been to show Dns configuration but maybe you did it on another video
Great Knowledge Video of DNS records I ever see
Wow, I liked it. Thanks for sharing this with us.
Thanks for watching.
Thank you. Excellent tutorial!
Thank you for your great feedback!
very well said :) thanks for all the videos
Can you make a video on different types of http error codes in the same whey.your videos are simple and easy to understand
Great video on common resource records!
Thanks!
Thank you. Very simple and informative way.
Glad it was helpful!
Competent video with brilliant rhetoric.
Thanks very much.
Congratulations! Nice video!
+Vinicius Thank you very much, we're glad to hear your feedback.
nice clear explanation with examples and with easy english
Thanks!
Thanks.
Great Video, helped explain a lot. Thanks :)
Thanks...It's been very very informative..!!
You're very welcome!
Thank you very much ,,it is very helpful.
Thanks, glad we could help.
superb,its really useful to me to understand
thanks a lot
+Balaji Raina You're most welcome.
Helpful indeed, clear explanation
Thanks for the great feedback and for watching!
Really helped me. Thanks for that.
You're welcome!
Finally found this
Thank you sir
Thanks for watching.
Very good videos with full clarity.Well done sir but no videos on AD DS backup and restore.pls upload sir.
Sorry about that, will get those videos done when we can.
thanks for the video! Learned a lot from it
Glad it was helpful!
I love it soo much, Cheers.
great it will help me on how to recognize those records in DNS
Glad we could help.
Nicely done 👏👏
Thanks!
thx alot , great video
Excellent! Thank you
+shubham joshi We're glad you think so! You're welcome and thank YOU for watching!
Thanks to explain DNS record in easy to understand
It's my pleasure
excuse me sir
i have a doubt
what do you mean by resource records?(my exam question)
ca i write your explanation for that question
thank u sir
thank you, excellent.
+roxriver91 You're welcome! Thanks for watching.
thanks again .. great video
You're welcome!
Great video
Thanks very much.
Thanks so much
No problem at all. Thanks for watching.
it's helpful thank you
You're welcome, glad the video was helpful!
well explained thanks !
You're very welcome!
I do everything right but the SPF record can't be verified so frustrating!
Great Video very well Expained Thx
Thanks very much and thanks for watching.
thanks so much!!
Amazing..Nice
very good!!thanks
So helpful!
Glad it was helpful!
thank you very much it really help me
Thanks for watching.
For CNAME Record where does it maintain ip for web1, cname stors alias but how is actual ip is obtained for web1, is another call made to another dns server which maintains a A record or same server maintains both CNAME and A record.
The resolver sees that it's a CNAME and begins its search over again at the root domain level. For example, if there is a DNS zone as follows:
NAME TYPE VALUE
--------------------------------------------------
bar.example.com. CNAME foo.example.com.
foo.example.com. A 192.0.2.23
when an A record lookup for bar.example.com is carried out, the resolver will see a CNAME record and restart the checking at foo.example.com and will then return 192.0.2.23.
This is great.
Excellent, thanks for the wonderful feedback.
Great stuff
Thank you!
THANK YOU
You're very welcome!
i have a live scenario..
Windows 2012 installed with AD and Dns. Standard configuration.
noticed
if i nslookup ip and hostname . all good
if i use the fqdn there is 2 request time out and a reply.
if i use fqdn with dot at the end its good.
please help
Thanks in advanc
Sri Rama I am not sure what the problem is here. Windows will normally add the dot at the end so you don't need to worry about it. It is strange that it requires it to be there. Have you configured your own root servers or are you forwarding the requests to your ISP?
thanks, it is helpful
Thank you for watching!
I am unable to ping Server 2K8r2 to win 7 host. I have created DNS forward and reverse records and allow ICMP also.
What happens when you try to ping the IP address directly?
it is valid 100% for the 70-411.
+LEF ISOS Excellent, we're always excited to confirm our content lines up with the Microsoft exams.
I am so confused.. what are the differences between the MX, pop3, Imap4, snmp, smtp?
DNS MX (Mail Exchanger) Record:
MX records are DNS records that specify the mail servers responsible for receiving email messages on behalf of a domain.
MX records help route email messages to the correct destination by pointing to the mail servers' hostnames or IP addresses.
MX records are essential for email delivery, as they determine where incoming email messages should be delivered within a domain.
POP3 (Post Office Protocol version 3):
POP3 is an email retrieval protocol used by email clients to retrieve email messages from a mail server.
POP3 typically downloads email messages to the client's device, removing them from the server. This means that emails are stored locally, and changes made on the client do not affect the server's copy.
POP3 is commonly used for downloading emails to a single device, like a computer.
IMAP4 (Internet Message Access Protocol version 4):
IMAP4 is another email retrieval protocol used by email clients to access email messages stored on a mail server.
Unlike POP3, IMAP4 allows multiple devices to access the same mailbox simultaneously and keeps emails synchronized across all devices. Changes made on one device are reflected on the server and other devices.
IMAP4 is suitable for users who want to access their emails from multiple devices and keep them synchronized.
SNMP (Simple Network Management Protocol):
SNMP is a network management protocol used for monitoring and managing network devices like routers, switches, and servers.
SNMP allows network administrators to collect data and manage devices remotely by querying and configuring settings on network equipment.
It is not directly related to email or DNS but is essential for network management and monitoring.
SMTP (Simple Mail Transfer Protocol):
SMTP is an email sending protocol used to send outgoing email messages from a client to a mail server or from one mail server to another.
SMTP is responsible for routing and delivering email messages to their intended recipients. It works together with MX records and other email protocols.
SMTP is essential for the delivery of email messages across the internet.
In summary, DNS MX records help route email messages, while POP3 and IMAP4 are email retrieval protocols for accessing email messages stored on mail servers. SNMP is a network management protocol, and SMTP is an email sending protocol responsible for delivering email messages. These protocols serve different roles in the email and network communication process.
4:10 did you mean when a DNS server has an email it needs to end it needs to locate a mail server
It is a little confusing. So essentially lets say that an e-mail server wants to send an e-mail to example.com. In order to do this, it needs to send the e-mail to the example.com mail server. So it performs a look up to find out where example.com mail server is. Essentially gets the MX record for example.com. The mail server then contacts the example.com mail server and transfers the mail to it.
great video
+Nithin Kg Thanks!
When you said "another A record", did you mean another Alias Record?
That's correct.
Thank you. Also, since PTR works the opposite of A records essentially, does that mean it also works the opposite of CNAME records?
The A record maps a name to one or more IP addresses, when the IP are known and stable.
The CNAME record maps a name to another name. It should only be used when there are no other records on that name.
The A name must resolve to an IP, the CNAME and ALIAS record must point to a name.
To answer your question: No, PTRs are not the opposite of CNAMEs. CNAMEs are similar to aliases and point to another hostname vs an A record which points to an IP.
thanks thanks
thanks thanks
Thank you I mean it u helped me
You're most welcome, thanks for watching!
How do I set up my server when I have it on a subnet? Say my external ip is 84.22.1.331 but my local ip is 192.168.1.2. How would I set up my www.website.com to be sendt to the server with the local ip of 192.168.1.2 ?
+Ragatokk Your server is using a private IP Address. So you need to configure your home router to forward web traffic to that server. So in your router, forward port 80 to 192.168.1.2
Thanks, but how do I do it when I have two servers on the same network?
+Ragatokk Multiple web sites can share the same IP Address. The web server should use the incoming DNS to work out what web site it is. However, you will not be able to have to servers using the same port unless you have two different public IP Addresses.
there's a difference between A Records and CName, CName can't be used for naked domain names.
CName are like a shortcut like that used in the file system. For example, if you had www.itfreetraining.com and itfreetraining.com you could create a CName to like one to the other. This way you only have one A record making it easier to manage.
nice.
thanks
You're most welcome!
Why there is not MX record when I nslookup www.hotmail.com ?
Hotmail seems to want to use a CNAME record vs a traditional MX record. That's probably why.
awesome
Thanks!
Nice
Thanks!
1.25 video speed is best
i dont know the use of this stupid service record .. its allways spam filessrv like this ::::::: Firefox Setup 16.0.1SrvSrvSrv .. and i dont know how to stop it .. it creat about 50 - 74 file when i start any program or click any icon :S any one can help me in this ?
Mohamed Abas I have not heard of this before. If you know which computer it is coming from I would do a check for the computer to see what software is installed. perhaps run a packet sniffer on the computer to work out which software is creating them. Perhaps it is Malware so I would do a check for that as well.
if they start training institute in indian many students will benefit
I'm studying computer networking for few weeks using web pages and youtube and I mostly encountered courses with indians (I hope that's how you call people from india) so I'm not sure if they even need teacher, since they are teacher itself :D Kidding, but sometimes they really are "know-it-all". Great video and explanations :) Peace
Out of everyhting from TCP/IP if find this topic the most difficult to remember !!!!
Networking isn't always intuitive so stick with it!
teaches better than Uni lol
Thank you.
Am I the only one who thinks DNS is confusing as hell been trying to learn it for about a month
DNS can be difficult at first, is there anything in particular you are having problems understanding?
Such a vague explanation
This is a pretty old video now. It helps if you watch the other DNS videos as well. We generally make the videos now so they can be watched by themselves. Is there anything in particularly you are having trouble understanding.
so confusing
What do you find confusing?
Your explanation of MX was very confusing.
What was confusing? Perhaps we can help clear up any confusion. :)
Pro tip: don’t use Microsoft technologies or products
Sorry but this is a terrible and hard to understand presentation for beginners. A more visual explanation of what's being said would've been helpful.
Sorry to hear that. We are currently redoing the way we do videos so future videos should be better.
Thanks very much.
Thank you.