Understanding DNS: Concepts and Operations
The dig command is a DNS client used to query DNS servers. It’s often used to detect problems in DNS server configuration. With dig, queries can be fully defined on the command line, or you can include them in a file and pass it as an argument to dig using the -f option. If no server is indicated, the servers to be consulted are assumed to be those listed in the /etc/resolv.conf file.
Caching DNS Servers
A caching-only DNS server handles client inquiries on behalf of domains. They do *not* contain any information about the zone and are used to speed up queries. They do not have any IP addresses associated with a name.
Named Daemon and Resolver
The named daemon is the domain name server; that is, it contains the database with information on a segment of the network and responds to requests. The resolver (client) generates the requests. It is a set of routines that allow clients to access the server to resolve the name to search for an address.
Host Computer
The host computer allows you to search the DNS. It is used to convert names to IP addresses and vice versa.
The resolver generates requests. It is a set of routines that allow clients to access name servers to resolve the IP address lookup by name.
Name Resolution
Name resolution is a mechanism that translates machine names given by the user to connect to remote servers into IP addresses. The user tries to connect from their local machine to a server that provides the remote URL. For this to be transformed into a specific IP address to access the remote server, the client machine consults the local DNS server to query or request the DNS. This request is carried out by resolvers from the DNS server machine. The local server responds, thus obtaining the IP for the remote server and accessing the site, all transparently to the user.
FQDN and TLD
- Fully Qualified Domain Name (FQDN): A name that includes the computer’s name and the domain name associated with that team.
- Top-Level Domain (TLD): The ending of a domain. These endings are called Top-Level Domains. They are usually two or more letters that correspond to a spatial code (based on ISO-3166) or a list of generic names.
Example: TLDs are used for Internet domain registration in Spain.
Domain Name System (DNS) is a hierarchical naming system for computers, services, or any resource connected to the Internet or a private network. This system associates various information with domain names assigned to each participant. Its most important function is to translate (resolve) names intelligible to humans into binary identifiers associated with networked computers, to locate and address these computers worldwide.
Resource Records (RR)
Each domain name authority has an associated resource record (RR) group. Each register contains the following fields:
- Domain Name: The name to which the resource belongs.
- Lifetime: The validity lifetime for registration or caching.
- Class: IN for Internet information.
- Type: The type of record.
- Value: A number or ASCII string depending on the type.
Difference Between Domain and Zone
- Domain: A subtree of the domain name space. It is a node with all nodes below it. The domain contains machines and other domains called subdomains.
- Zone: A file that contains records from the domain name space database. Zones can identify one or more domains and address customer requests. Authority over the zone refers to the parts of the domain that the name server is authoritative for.
Delegation
Delegation is defined as a mechanism to decentralize the administration of the DNS database by dividing the domain into subdomains and ceding control of each subdomain to another authority. The current condition of the resource records of that subdomain is transferred.