DNS Overview

A Domain Name System (DNS) is a distributed hierarchial system that converts hostnames to IP addresses. The DNS is divided into sections called zones. Each zone has name servers that respond to the queries belonging to their zones.

This topic includes the following sections:

DNS Components

DNS includes three main components:

DNS Server caching

DNS name servers are responsible for providing the hostname IP address to users. The TTL field in the resource record defines the period for which DNS query results are cached. When the TTL value expires, the name server sends a fresh DNS query and updates the cache.

Forwarders

When a DNS server cannot resolve a query, it forwards the query to another DNS server that is configured as a forwarder. You can use the CLI to configure a DNS server to act as a forwarder. The DNS server forwards the queries only to the servers that are configured as forwarders.

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