DNS Basics
Last updated
Last updated
What are the DNS Record Types?
What is a zone transfer?
A zone transfer is the process of replicating all the DNS records from the SOA (Start of Authority)
🚨 Note: Administrators need to be careful about which IP addresses are allowed to perform a zone transfer. Most admins restrict this to a small list of name servers inside their network
Two types of DNS Servers
Name resolvers - simply answer requests
Authoritative servers - hold the records for a namespace, given from an administrative source, and answer accordingly
What information does the SOA record provide?
Source Host - hostname of the primary DNS server for the zone (also an associated NS record)
Contact e-mail - email address of the person responsible for the zone file
Serial number - revision number of the zone file. This number goes up every time the zone file changes, secondary servers use this to know when they need to update their copy (if the SN is higher than the one of the secondary server, they need to update)
Refresh time - The amount of time a secondary DNS server will wait before asking for updates. Default is 3600 seconds (1 hour)
Retry time - Amount of time a secondary server will wait to retry if the zone transfer fail. Default if 600 seconds.
Expire time - Max amount of time a secondary server will spend trying to complete a zone transfer. Default is 86,400 seconds (1 day)
TTL - minimum "time to live" for all records in the zone. If not updated by a zone transfer, the records will expire. Default is 3600 seconds (1 hour)
What are the five regional Internet Registries (RIRs)?
American Registry for Internet Numbers (ARIN) - Canada, Caribbean and North Atlantic islands, and the USA
Asia-Pacific Network Information Center (APNIC) - Asia and the Pacific
Réseaux IP Européens (RIPE) NCC - Europe, Middle East, and parts of Central Asia / Northern Africa
Latin America and Caribbean Network Information Center (LACNIC) - Latin America and the Caribbean
African Network Information Center (AfriNIC) - Africa