DNS Servers #

A DNS server is a computer running DNS server software.

• Protocols: Primarily UDP but sometimes TCP
• Port: 53

Root Servers #

• DNS starts with a ‘.’
• Delegates name resolution to other DNS servers

Top-Level Domain (TLD) Servers #

• These are all the ‘.com’ ‘.org’ ‘.net’ ‘.edu’ ‘.gov’, etc.
• ICANN has the authority to create new TLDs.

Second-Level DNS Servers #

Handle millions of names like totalsem.com, alexkraker.net, etc

Name Servers #

DNS Zone #

• Foward Lookup Zone Where IPs and FQDNs for the devices in a domain are stored.
• Reverse Lookup Zone
• Cached Lookups Previously resolved FQDN ’s are cached.

Configuration #

• Authoritative Store IP addresses and FQDN’s of systems for a particular domain or domains.
• Cache-only Never the authoritative nameserver. Communicate with other DNS servers to resolve domains.

DNS Records #

Location of DNS Servers #

• Local
  • Usually private DNS
  • Typically forwards DNS for which it’s not the authoritative nameserver
• External Any DNS server that is not internal to an organization.

Dynamic DNS #

Works together with DHCP to dynamically update IP addresses of forward lookup zones

• IPAM IP Address Management Protocol used to establish DNS when IP addresses change. Used to communicate between DHCP and DNS server.