DNS Server Configuration

grr i have four different gps apps again

DNS is very very very very very very very∞ important to the functionality of the Internet. Things like Active Directory and most Linux networks need a DNS service somewhere in order to work. However, there are still multiple types of DNS servers.

DNS servers are usually configured to run on 53/udp, and some also listen on the same TCP port. Opening the TCP port allows for larger record transfers with packet sizes beyond the 512-byte limit, in use cases like DNS for IPv6 or when a security protocol is deployed on the network (e.g. DNSSEC).

Zones

Nameservers have two types of zones, primary and secondary. Primary zones store editable records, while secondary zones have copies of readonly records, maintained through a replication process called zone transferring from a primary name server. Secondary zones are usually stored on multiple servers to provide fault tolerance and load balancing.

Nameservers that have complete records for a domain are called authoritative. Primary and secondary name servers are authoritative.

Servers that don't maintain any zone are cache-only nameservers. Non-authoritative queries are results from cached records, rather from an authoritative server with a complete records.

Caching

Each record stored on a nameserver has a default TTL (time-to-live) value. This value tells the server how long to keep this record cached. Low TTL values allow for frequently updated records, but increased server load and resource consumption.