< turn > Detailed DNS Common records (bottom): DNS Series III

Source: Internet
Author: User
Tags mx record nslookup nslookup tool to domain fully qualified domain name

In the previous blog post we introduced several indispensable records in DNS servers, including a, NS, and SOA records. In this blog post we will continue to introduce several other common DNS records, I hope you can understand the DNS helpful.

Four MX record

MX records are also known as Mail Exchanger Records, and MX records are used to indicate which server is the mail server for the current zone, for example, in the hexun.com zone, mail.hexun.com is a mail server, and the IP address is Then we can do the following processing in the DNS server:

1. Create a record for mail server

As shown, we first create a record for the mail server, because the MX record does not use an IP address when describing the mail server, only the fully qualified domain name can be used.

2. Create MX record

As shown in, select Create MX record in the DNS server.

As shown in the MX record, this MX record illustrates that mail.hexun.com is a hexun.com mail server with a priority of 10. Note that if the hexun.com region has more than one MX record and the priority is different, the other post office sends the message to hexun.com first to the highest priority mail server, and the lower the priority number, the higher the priority, and the highest priority is 0.

MX records are essential for mail servers, and two Internet post office systems must rely on DNS MX records to locate each other's mail server locations when communicating with each other. For example, the 163.net Post Office sends an e-mail to the 263.net Post Office, the SMTP server of the 163 post office needs to issue a query request to the DNS server, ask the DNS server to query the 263.net MX record, so that 163 post Office SMTP server can locate the 263.net SMTP server, but Then you can send the mail to the 263 post Office.

We use an example to specify the purpose of the MX record, we built a mail server on the, we used this mail server to [email protected] send an e-mail, When the mail server sends mail to the Sohu.com Post Office, we use the Grab kit tool ethereal to record the packet capture process. As shown, We can see that the mail server sends a query request to the DNS server when the message is sent, requests that the Sohu.com MX record be queried, and the DNS server tells the requester that the Sohu.com Post Office's mail server is sohumx.h.a.sohu.com, so that 192.1 68.0.109 only knew that the mail should be sent to sohumx.h.a.sohu.com.

Five Cname record

A CNAME record is also known as an alias record, which is to make a server have multiple domain names, which is roughly equivalent to a nickname for a person. Why do I need a CNAME record? On the one hand is to take care of the user's habits, such as we are accustomed to the mail server named Mail, the FTP server named FTP, if there is only one server, while providing mail services and FTP services, then how exactly should we name it? We can name the server mail.hexun.com, and then create a CNAME record called ftp.hexun.com to both. In addition to the use of CNAME records also have security considerations, such as we do not want others to know the real domain name of a site, we can let users visit the site alias, such as the Baidu website we visit the real domain name is [url]www.a.shifen.com[/url], The [Url]www.baidu.com[/url] we use is just an alias for [Url]www.a.shifen.com[/url].

OK, so here's an example of creating a CNAME record, assuming we want to create an alias ftp.hexun.com for mail.hexun.com, we can do the following. As shown, we chose to create a CNAME record in the DNS server.

Record content as shown, we created an alias record for mail.hexun.com, which is ftp.hexun.com.

Parsing the ftp.hexun.com, as shown in the DNS server tells us that ftp.hexun.com is mail.hexun.com.

Six SRV record

An SRV record is an abbreviation for a server resource record, an SRV record that is a fresh face in a DNS record, and an SRV record is defined in RFC2052, so many older DNS servers do not support SRV records. So what's the use of SRV records? The role of SRV records is to describe what kind of service a server can provide! SRV records are important in Microsoft's Active Directory, and you know that there is not much to do with DNS in the NT4 age domain. But starting from the Win2000, the domain can not be separated from the help of the DNS, why? Because computers within a domain rely on the SRV records of DNS to locate domain controllers! Microsoft Instant Messaging Server Live Communications server can also rely on SRV records to locate an Instant Messaging server, and since SRV records can locate specific servers, we can expect that SRV records will play a more and more role in Microsoft's future server offerings.

Here we give an example of the role of SRV records, assuming that web.hexun.com is a Web server in the hexun.com domain, Web.hexun.com provides Web services on port 80, how do we use SRV records to describe this information? As shown, in the DNS server, we select Create another new record.

Record type we select SRV.

Is the SRV record we created, which means that server web.hexun.com provides HTTP services in the hexun.com domain, which is based on the TCP protocol, which is guarded on port 80.

Seven PTR record

PTR records are also known as Pointer Records, and PTR records are the reverse record of a record, which is the role of resolving IP addresses to domain names. As we mentioned earlier, the reverse zone of DNS is responsible for parsing from IP to domain names, so if you are creating PTR records, you must create them in the reverse zone. Here's an example of how to create a reverse region and a PTR record.

As shown, we select New zone in the reverse zone of the DNS server.

The New Zone wizard appears and select next to continue.

Region type Select Primary zone.

The wizard requires the current network number, the network number is the IP address and subnet mask after the operation of the result, the name of the reverse zone can not be arbitrarily set, must be reversed network number plus in-addr.arpa suffix. For example, the current network number is 202.99.16, and the name of the reverse zone should be 16.99.202.in-addr.arpa.

Set the data file for the reverse zone, using the default values.

This area also does not require dynamic updates.

As shown, the reverse zone creation is complete.

Once the reverse region has been created, we can create a PTR record in the reverse region, as shown in we chose to create a PTR record in the reverse region.

As shown, the PTR record we created resolves to the domain name ns1.hexun.com.

After we have created the PTR record, we can resolve the IP to the domain name, which is the result of our testing with the Nslookup tool, and we see that the IP address has been correctly parsed into the domain name. In fact, when we run Nslookup, the first thing nslookup do is to reverse-parse the DNS server's IP address

At this point, we have a number of common DNS server records are simply introduced, if you have mastered, then to deal with general application is basically no problem. In subsequent Active Directory series posts, we will continue to see the important role of DNS in AD.

This article is from the "Yuere Microsoft Online Classroom" blog, make sure to keep this source http://yuelei.blog.51cto.com/202879/107676

< turn > Detailed DNS Common records (bottom): DNS Series III

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