Domain Names / DNS

What is FQDN?

Fully Qualified Domain Name: sometimes also referred as an absolute domain name is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS).

What is TLD?

Top Level Domains.

What is 8.8.8.8?

Google DNS is a public DNS service that is provided by Google.

8.8.8.8: the primary DNS server for Google DNS.
8.8.4.4: the secondary DNS server.

CloudFlare's public DNS resolver: 1.1.1.1.

What is Multicast DNS?

In computer networking, the multicast DNS (mDNS) protocol resolves hostnames to IP addresses within small networks that do not include a local name server. It is a zero-configuration service, using essentially the same programming interfaces, packet formats and operating semantics as unicast Domain Name System (DNS). It was designed to work as either a stand-alone protocol or compatible with standard DNS servers.

What is SRV record?

The DNS "service" (SRV) record specifies a host and port for specific services such as voice over IP (VoIP), instant messaging, and so on. Most other DNS records only specify a server or an IP address, but SRV records include a port at that IP address as well.

What is SOA record?

A Start of Authority (SOA) record is a DNS record that stores administrative information about a domain or zone. This information includes:

The domain's primary name server
The domain's responsible party, such as an email address
A timestamp of the last domain update
The number of seconds before the zone should be refreshed
A time period for secondary name servers to retry zone transfers after a failure

SOA records are required for all DNS zones to comply with IETF standards. They are also important for zone transfers. A new SOA record is needed whenever a new zone is set up or a DNS zone is transferred.

To check SOA records, use dig:

$ dig google.com SOA