Question 1

What is an IP address?

Accepted Answer

Every computer on the Internet identifies itself with an “Internet Protocol” or “IP” address, which is a series of numbers — just like a phone number. That means you can contact any of those computers by typing in the website name, or you can type the IP address into your browser address bar. Either method will get you to the same destination. All servers that host websites and apps on the internet have IP addresses, too.

Question 2

What is the domain name system (DNS)?

Accepted Answer

The domain name system (DNS) is sometimes referred to as the “phone book” of the Internet.  You can connect to our website by typing in the IP address in the address bar of your browser, but it’s much easier to type in umbrella.cisco.com. DNS was invented so that people didn’t need to remember long IP address numbers (like phone numbers) and could look up websites by human-friendly names like umbrella.cisco.com instead.

Question 3

What is an authoritative DNS nameserver?

Accepted Answer

This type of DNS server holds a copy of the regional phone book that matches IP addresses with domain names. These are called authoritative DNS servers. Authoritative DNS nameservers are responsible for providing answers to recursive DNS nameservers about where specific websites can be found. These answers contain important information for each domain, like IP addresses.

Like phone books, there are different authoritative DNS servers that cover different regions (a company, the local area, your country, etc.) No matter what region it covers, an authoritative DNS server performs two important tasks. First, it stores lists of domain names and their associated IP addresses. Second, it responds to requests from a recursive DNS server (the person who needs to look up a number) about the correct IP address assigned to a domain name. After getting the answer, the recursive DNS server sends that information back to the computer (and browser) that requested it. The computer connects to the IP address, and the website loads, leading to a happy user who can go on with their day.

Question 4

What is a recursive DNS server?

Accepted Answer

When you type a website address into your browser address bar, it might seem like magic happens. In reality, the DNS system makes effortless internet browsing possible. First, your browser connects to a recursive DNS server. There are many thousands of recursive DNS servers in the world. Many people use the recursive DNS servers managed by their Internet Service Provider (ISP) and never change them. If you’re a Cisco Umbrella customer, you’re using our recursive DNS servers instead.

Once your computer connects to its assigned recursive DNS server, it asks the question “what’s the IP address assigned to that website name?” The recursive DNS server doesn’t have a copy of the phone book, but it does know where to find one. So it connects to another type of DNS server to continue the search.

Question 5

Why do we need the domain name system (DNS)?

Accepted Answer

Without DNS, the internet stops working. The DNS system is so important to the modern world that we often refer to it as the foundation of the internet. If your recursive DNS service breaks for some reason, you won’t be able to connect to websites unless you type in the IP addresses directly — and who keeps an emergency list of IP addresses in their desk? If the recursive DNS service you use is working, but has been slowed down for some reason (like a cyberattack), then your connection to websites will be slowed down, too.

What is the difference between authoritative and recursive DNS nameservers?

DNS-Layer Security: The Ultimate Guide to What It Is and Why You Need It

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