Name records for DNS

Source: Internet
Author: User
Tags mail time interval mail exchange linux

In fact, DNS is not just a way to interpret addresses, but also to answer more information about the network and the host. One of the most important features is the ability to route mail systems. This information is usually present in the DNS data file with a different "record" name.

Let's refer to a Linux DNS file to see how these records are represented.

; Zone file for siyongc.domain
; Then full zone file
$TTL 86400
@ IN SOA redhat52.siyongc.domain. netman.siyongc.domain. (
1999092801 ; serial
8H ; refresh
2H ; retry
1W ; expire
1D ) ; minimun
IN TXT "A test domain, created by Netman"
IN NS redhat52
IN NS debian.home.
IN MX 10 redhat52.siyongc.domain.
IN MX 20 debian.home.
localhost IN A

gw IN A
IN HINFO "Redhat" "MASQ"
IN TXT "The masquerade gateway to internet"

redhat52 IN A
IN MX 10 redhat52
IN MX 20 debian.home.
IN HINFO "Dell PII 266" "Linux RedHat"
www IN CNAME redhat52
mail IN CNAME redhat52
ftp IN CNAME redhat52
news IN CNAME redhat52
smtp IN CNAME redhat52

pii266 IN A
IN MX 10 redhat52.siyongc.domain.
IN MX 20 debian.home.

slware36 IN A
IN MX 10 redhat52.siyongc.domain.
IN MX 20 debian.home.

rhroute IN A
IN MX 10 redhat52.siyongc.domain.
IN MX 20 debian.home.

Let's just ignore the lines at the beginning. That is for the DNS system itself (I will discuss it in detail in the "Learning Linux" article) here we are looking at a few record names.

Category name represents meaning
TXT is just some description text can be used to describe the host/network environment settings
The NS name server is the DNS server name specified by the zone
The MX Mail server is responsible for mail delivery via DNS queries. The advantage is that if you want to change the mail server, you can simply modify the DNS records and the other person's mail server does not care about which computer you are using to take charge of the mail exchange. You can also specify multiple mail servers to share the number of mail exchange work at the back of the MX specifies that the lower-order numbers for the server are preferred.
A used to correspond to the host name and its IP address, one of the most common and important records of this record.
HINFO and TXT are almost answers to the "Host information" query.
CNAME is an "alias" record that can use another (or more) name for a record to query outside. CNAME can correspond to a record but does not encourage a corresponding CNAME record.
AAAA and a records only correspond to the IP V6 format

Sharing DNS Work

The Primary (master) DNS server is a master control server that is primarily authorized to control all name records under a certain network domain and has the record data that governs all the domain records. Only Primary (master) can be modified.

But if the DNS server becomes very busy on a larger network, you can set up multiple DNS to share master's work but you may not want to go to every DNS server to update the data, and even if you are willing to do so it is prone to errors or data synchronization situations. This allows you to set other servers for secondary (slave) DNS to master the record data so that other computers can be assigned to different DNS to do the query can share master's work and the data can be automatically synchronized work. You can set the time interval for DNS data synchronization to be set at the Refresh setting in the DNS file. You will also see serial when Slave's serial number is less than its data will be ignored.

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