The top down or bottom up nature of DNS depending on your perspective, it one of the main points of the DNS system. Learn how the hierarchy of DNS is a major component of it's reliability. Learn how the distribution of information works in DNS. Learn about Root servers, name servers, domains and zones, and subdomains.
- [Voiceover] The DNS Hierarchy is fundamental to how DNS works and I think that it might be easier for you to understand how it works and what it is if we look at it in pictures so we're gonna start here, the world wide internet, right, and it functions because DNS is able to keep all of these top-level domains organized under root servers. The root servers are responsible for holding information about all of the top-level domains. So the root servers, what are they? Well they're servers that are administered by the IANA and that's the Internet Assigned Numbers Authority and you can easily lookup on the IANA website all of their original top-level domains and all of the infrastructure top-level domains and country code top-level domains and all of the new commercial top-level domains, there's a whole ton of them.
It's just unbelievable how many there are and they're all located and tracked inside of those root servers, right? Okay, so those root servers contain top-level domains but what are the top-level domains? Well these are things like the com and org and gov and UK stands for everybody in Great Britain and the United Kingdom. App is one of the newer ones that's been approved, right, there's an entire .app domain and all of these things are maintained by the root servers. The root servers know what they are and how to find them, that's why whenever a DNS resolver is looking to figure out stuff that's inside of a top-level domain, they have to go to the root servers first in order to figure out which server is responsible for .com, which one's responsible for .org and then those hold on to domains, right, so each of those like com would hold, I've got four in a box here obviously, but there's more than that, way, way more and so each of these is responsible for keeping track of the location in terms of name servers and IP addresses and how to locate each of the name servers for those domains.
So now what's a domain? Well, the domains that are inside of each of those boxes would be things like our landonhotels.com, right, Landon Hotels is a resource that's sitting inside of that .com container, so .com is responsible for keeping track of it, it sits in there, okay? Now within that, you can even have subdomains, right, so each domain can be responsible for keeping track of an entire subdomain within that domain. So what would be a good example of that, well, in another video I had discussed the possibility of having an entire set of wikis at landonhotels.com.
Well that's fine, each of those wikis could be located inside of a subdomain and there could be a domain name server responsible for that subdomain zone being wikis, and so that would give you an entirely other container in which to store additional groups of things, right, so that subdomain of wikis.landonhotels.com could contain lots of different servers that might be wiki1.wikis.landonhotels.com and it just continues to build from there on up.
So that is the hierarchy, there are so many of these things that it's a miracle that we're keeping track of all of them honestly. The internet is an incredibly complicated place and this is part of how we keep it all organized under the DNS Hierarchy.
To begin, author Sean Colins covers the fundamentals of DNS. He then segues to more complex topics such as setting up a DNS server on Linux, Mac, and Windows and working with DNS record types, such as AAAA, MX, TX, CNAME, and SPF. He offers breakdowns of difficult concepts as well as practical technical tips for the day-to-day activities involved in DNS server management.
- How split-horizon DNS works
- Lookups in Network Utility and Terminal on OS X, and from the cmd prompt on Windows
- Resolving DNS from different DNS servers, including BIND on pfSense and DNS Manager in Windows Server 2012
- Query, recursion, and caching basics
- DNS hierarchy
- Root-level DNS servers
- Configuring resource records: AAAA, MX, TXT, and more
- DNS tips and tricks for BIND, Windows Server, and Mac OS X Server
- Exploring DNS server options