In order to find resources on the network, computers need a system to look up the location of resources. Check out http://YouTube.com/ITFreeTraining or http://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.
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.
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).
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“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” http://en.wikipedia.org/wiki/SRV_record
thx alot , great video
Great job.. a value added would have been to show Dns configuration but maybe you did it on another video
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.
Excellent right to the point explanations. Thanks a lot!
great it will help me on how to recognize those records in DNS
thank you very much it really help me
Out of everyhting from TCP/IP if find this topic the most difficult to remember !!!!
When you said "another A record", did you mean another Alias Record?
there’s a difference between A Records and CName, CName can’t be used for naked domain names.
Why there is not MX record when I nslookup http://www.hotmail.com ?
I am unable to ping Server 2K8r2 to win 7 host. I have created DNS forward and reverse records and allow ICMP also.
You are truly amazing. THANK YOU.
You have a collection of great videos. Very informative!
Helpful indeed, clear explanation
Nicely done 👏👏
Thank you I mean it u helped me
Thank you friend ! it was really nice Vedio. I have one more scenario question I need your help : I have two DC 1 and DC2 . and DC1 is primary domain and DC 2 is secondary detail. I have two types of authentication services 1) Service account authentication 2) General user authentication. I wanted to give service account authentication load on the DC1 and general authentication load should be authenticated by DC2. may I know the step by step configuration to do that ? please share me vedio if possible. thanks in Advance! Regards,Jaishree Guptapinko.firstname.lastname@example.org+91-9008510832
I recommend dynu.com for free DNS record hosting. They offer hosting for all DNS records mentioned in the video for free: A, AAAA, MX, SRV, SOA, CNAME, NS as well as TXT, DKIM etc.
Thank you. Very simple and informative way.
Great Knowledge Video of DNS records I ever see
1.25 video speed is best
Thank you for the clear and concise lesson! So helpful!
i still watch ur awesome expalnations, and it is jus so good.
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!
4:10 did you mean when a DNS server has an email it needs to end it needs to locate a mail server
Finally found this
Thank you sir
This is great.
Thank you. Excellent tutorial!
Thanks…It’s been very very informative..!!
thanks again .. great video
thanks, it is helpful
Can you make a video on different types of http error codes in the same whey.your videos are simple and easy to understand
You got the art of explaining, you are the best
Your explanation of MX was very confusing.
Great video on common resource records!
teaches better than Uni lol
Wow, I liked it. Thanks for sharing this with us.
I do everything right but the SPF record can’t be verified so frustrating!
Really helped me. Thanks for that.
thanks for the video! Learned a lot from it
well explained thanks !
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