Definition - Domains vs. Zones
A DNS zone is any distinct, contiguous portion of the domain name space in the Domain Name . Tools. What links here · Related changes · Upload file · Special pages · Permanent link · Page information · Wikidata item · Cite this page. This page explains the key concepts of domains, DNS zones, and DNS . They are used in multiple applications, in particular related to email. A DNS zone is an administrative space which allows for more granular control of DNS components, such as authoritative nameservers. The domain name space.
Primary and secondary name servers are both considered as authoritative for a domain. DNS Zones provide a very easy and simple method of grouping domain data from multiple domains together for storage.DNS Zones
For domains to share a zone and hence a zone file the domains must be contiguous. A domain administrator would be responsible for creating zones, and delegating responsibility for these zones to an administrator and DNS server. To illustrate we will refer to the diagram below which shows a section of the domain name system which has been divided into 3 zones.
You should note that you cannot create a zone that includes Domain1 sub domain 1 and Domain 3 because they are not contiguous. Zone File Storage In our analogy the data is stored on a paper list and kept by the team manager. A zone file is a text based file with a format defined in RFC and and is stored on a DNS server name server.
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Zone files contain the IP and name data, MX records and other service records. They also contain glue data that connects them to the other DNS servers. Referring to the diagram above the DNS server responsible for zone 1 will contain records that tell it: Which DNS servers have data for Domain2.
Which DNS servers have data for Domain3 sub domain1 i. List of Root servers root hints List of forwarding servers if using forwarding The DNS server responsible for Domain 1 -sub domain 1 and 2 — i.
Zone 2 has no knowledge of who has data for domain3 sub domain1 — i. The SOA start of authority must be present in a zone file, and defines the domain global values mainly to do with zone transfer. An example record is shown below. Zone Delegation When an administrator of a domain decides to allocate responsibility of a child domain to someone else e.
Domains and Zones
This means that the zone file is stored on another DNS server than the parent domain. However the parent domain will keep track on the location of the zone by creating glue records to the name servers responsible for the zone data.
We saw this with Bill Needing to know who had the list for Teams A. Caching and TTL Caching is the process of temporarily storing data and is used frequently in networking, and on the Internet. Consequently, the name was officially redefined as an acronym for Address and Routing Parameter Area.
It contains sub-zones used for reverse resolution of IP addresses to host names IPv4: Although the administrative structure of this domain and its sub-domains is different, the technical delegation into zones of responsibility is similar and the DNS tools and servers used are identical to any other zone. Sub-zones are delegated by components of the respective resources. When an ISP allocates a range to a customer, it usually also delegates the management of that space to the customer by insertion of name server resource records pointing to the customer's DNS facilities into their zone, or provides other management tools.
Allocations of single IP addresses for networks connected through network address translation NAT typically do not provide such facilities. It begins with a list of addresses for the most authoritative name servers it knows about — the root zone name servers indicated by the full stop or periodwhich contains name server information for all top-level domains of the Internet.
Correct configuration of SPF records is important to prevent recipients from marking your email as junk. This ambiguity led to confusion, which was resolved by RFC It also states that the SPF record type is deprecated. The obsolete SPF record type isn't supported.
The service and protocol must be specified as part of the record set name, prefixed with underscores. The priority, weight, port, and target are specified as parameters of each record in the record set. The DNS standards permit a single TXT record to contain multiple strings, each of which may be up to characters in length.
Where multiple strings are used, they are concatenated by clients and treated as a single string. When using the Azure portal, PowerShell or CLI interfaces you should specify a single string per record, which is automatically divided into character segments if necessary. A TXT record set can contain multiple records, each of which can contain multiple strings. Tags and metadata Tags Tags are a list of name-value pairs and are used by Azure Resource Manager to label resources.
Azure Resource Manager uses tags to enable filtered views of your Azure bill, and also enables you to set a policy on which tags are required. For more information about tags, see Using tags to organize your Azure resources.
It does not support tags on DNS record sets, although as an alternative 'metadata' is supported on DNS record sets as explained below. Metadata As an alternative to record set tags, Azure DNS supports annotating record sets using 'metadata'. Similar to tags, metadata enables you to associate name-value pairs with each record set. This can be useful, for example to record the purpose of each record set. Unlike tags, metadata cannot be used to provide a filtered view of your Azure bill and cannot be specified in an Azure Resource Manager policy.
Etags Suppose two people or two processes try to modify a DNS record at the same time. And does the winner know that they've overwritten changes created by someone else?
- Definition - Domains vs. Zones
- Overview of DNS zones and records
- DNS Zones and Zone Files Explained
Azure DNS uses Etags to handle concurrent changes to the same resource safely. Etags are separate from Azure Resource Manager 'Tags'. Each DNS resource zone or record set has an Etag associated with it. Whenever a resource is retrieved, its Etag is also retrieved. When updating a resource, you can choose to pass back the Etag so Azure DNS can verify that the Etag on the server matches.
Since each update to a resource results in the Etag being regenerated, an Etag mismatch indicates a concurrent change has occurred. Etags can also be used when creating a new resource to ensure that the resource does not already exist.
The optional -Overwrite switch can be used to suppress Etag checks, in which case any concurrent changes that have occurred are overwritten.