The DNS

en:The DNS ja:DNS zh:DNS de:Das DNS he:ה-DNS ro:DNS ru:DNS pl:DNS ar:نظام أسماء النطاقات nl:De DNS-server it:Il DNS pt:O DNS es:El DNS fr:Le DNS

Description

The most common use of a DNS is to match a field to an IP address. It would be possible to navigate using addresses IP, but this would be less user friendly.

To contact a site, there is a resolution of field What translates the ip address.

The Servers DNS

A 'Server DNS provides the DNS service by definition. Most internet service providers /Web hosts provide a DNS service with recursion.

Following the reservation of a name of field, you will need a Server DNS where its DNS zone is registered. We are talking about in this case of Server name (NS).

DNS recursion

When a Server DNS is queried for the resolution of a name of field what he doesn't know, he asks another Server DNS for resolution. He kept this information in its cache.

Attention: DNS recursion can be diverted to make the 'DDOS DNS amplification'. It must therefore allow the use of this service only to trusted clients.

Server NS

It comes from Servers that contain a DNS zone field. These Servers are declared responsible for the first level of the extension register (.fr, .com...).

How to determine the Servers NS a DNS zone

For example we want to determine this for "'ikoula.wiki"'. As a first step consult a Server DNS root to determine what Servers DNS contain extensions area "'.wiki ' ' :

$ dig -t NS wiki @a.root-servers.net

;; AUTHORITY SECTION:
wiki.                   172800  IN      NS      a.nic.wiki.
wiki.                   172800  IN      NS      b.nic.wiki.
wiki.                   172800  IN      NS      c.nic.wiki.
wiki.                   172800  IN      NS      d.nic.wiki. 

Then he must consult the DNS of the extension to determine what are the Servers of our domain :

$ dig -t NS ikoula.com @a.nic.wiki

;; AUTHORITY SECTION:
ikoula.com.             172800  IN      NS      ns4.ikoula.com.
ikoula.com.             172800  IN      NS      ns5.ikoula.com.

The main type of DNS records

SOA

The registration of type SOA (Start Of Authority ) contains several important as information the Server NS primary, contact e-mail address, and the serial.

A

Records of type A (for host address ) are mappings between a host name and an address IPv 4.

YYYY

Records of type yyyy are the mappings between a host name and an address IPv 6.

CNAME

Records of type CNAME (Canonical NAME or CNAME ) are mappings between a host name and a different host name. It helps to have the same IP match the hostname defined in value. Define a CNAME at the root of a DNS zone is not permitted.

MX

The record type MX (Mail eXchanger ) sets the host name of Server Messaging and a priority. When multiple MX records are present in the same area, the MX with the lowest priority takes precedence. If the Server Priority MX is faulty, the Server With the lowest priority MX which is non lacking is used.

NS

Records of type NS (Server name or Server name ) identify the Servers DNS from the DNS zone. One of them must be the primary and is set in the SOA record, but the entirety of Servers NS of a DNS zone must be reported to the responsible for the first level of the extension registry.

TXT

The TXT record is used among other for :

- validate the property of a site ("' Example : GoogleAnalytics ' ' ).

- define the ServerMessaging s allowed to relay emails for your domain (’’’SPF’’’)

- define a public key for the encryption of e-mail ("'DomainKeys"' )

SRV

Records of type SRV (service) used to map a hostname to a given service type. Thus the SRV records can retrieve a list of Servers HTTP or domain controllers. It is possible to give different priority to every SRV record.

The principle of DNS replication

The DNS server change should be present on the Server NS primary.

In order for this change replicates, the serial must be incremented.

So the Servers secondary NS recover the DNS on the primary NS zone, should be :

- have a serial in the SOA in the primary DNS server of NS zone that is greater than the serial of the SOA of the zone on the secondary NS

- only the Servers secondary NS are allowed on the Server primary to make zone transfer. This is a DNS AXFR query.

To verify that replication in many was effective there are different site, including : whatsmydns This allows to check the current status of the DNS propagation after changing names of Servers. To do this, simply return the field be desired in the field provided for this purpose.

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