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Networking - DNS

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Lesson Description


Lession - #1381 DNS Zones


Domain Name System( DNS>
is divided into many multiple various zones. These zones distinguish between specifically managed areas within DNS namespace.

Domain Name System( DNS>
Zones is any distinct, connecting segment of domain name space in Domain Name System( DNS>
for which executive responsibility has been delegated to single administrative space which allows for more smooth control of DNS components. Namespace of web is organized into hierarchical layout of subdomains below DNS root domain. Individual domains of this tree may function as delegation points for administrative authority and management.

DNS zones are hierarchical concept. thus, namespace is subdivided into areas( zones>
for this purpose. The purpose of DNS zones is to permit easier control over multiple levels of website.

As the number of resource records increases for single sphere, it becomes complex to manage all of them. Network administrations moderate this issue by breaking down their configurations into multiple zones.

Root name servers are responsible for root zone. Each TLD name server is responsible for zone covering its specific TLD, and authoritative name servers are responsible for some even smaller zones below that.

The root and TLD name servers are actually just authoritative name servers, but, zones that they ’re authoritative for are special cases.

DNS zones are n’t necessarily physically separated from each other; zones are strictly used for delegating control.

Zone files

Zones are configured through what's referred to as zone files, that contain an actual representation of zone, simple configuration files, that declare all resource records for specific zone. A zone file needs to contain an SOA or Start of Authority resource record declaration and Global Time to Live( TTL>
. This SOA record declares zone and thus name of name garçon that’s authoritative for it. Global Time to Live( TTL>
, states for how records should be kept in local DNS cache. Along with SOA record and TTL, you ’ll generally find NS records that indicate other name servers which will even be liable for this zone. The format of zone file is defined in RFC 1035 and 1034.

DNS zone train comprises of directives and resource records.

Directives begin with a$.
There are three Directives


TTL – Time to Live value for zone.
ORIGIN – Defines base name- used in sphere name negotiation
INCLUDE – Include a train

$ TTL directive must be present at top of zone train before SOA record. While talking about zone lines, it’s imperative to know about Rear Lookup Zone.

Rear Lookup Zone

A rear lookup zone contains mapping from an IP address to host( contrary function of utmost DNS zones>
. These zones are used for troubleshooting, spam filtering, and bot discovery.

Just like how subdomains can go numerous layers deep, zones are frequently constructed to have numerous layers too, a bit like subdomains, although it’s rare to see certain zones deeper than just many situations.