Understanding the Role of DNS in Network Connectivity 🌐

The Importance of DNS for ISPs and Businesses 🏢

Having a reliable and functional DNS system is crucial for seamless network operations. Internet Service Providers (ISPs) often provide access to a recursive name server as part of their service, which is typically all that's needed for general internet communication.

However, businesses often run their own DNS servers to resolve names of internal hosts, such as nais-laptop or printer names, rather than relying solely on IP addresses.

Exploring Public DNS Options 🕵️‍♂️

A third option is to use a DNS-as-a-Service provider. This approach is becoming increasingly popular, and it can serve as a helpful backup or troubleshooting tool.

The Mystery of Level 3's Public DNS 🤔

In the ancient sysadmin lore, the most commonly used public DNS servers were those run by Level 3 Communications, one of the largest ISPs in the world. The IP addresses for these servers are 4.2.2.1 through 4.2.2.6, and they've been available for public use for nearly 20 years, despite Level 3 never officially acknowledging or advertising the service.

Google's Public DNS 🔍

Another popular public DNS option is Google's public name servers, with the IP addresses 8.8.8.8 and 8.8.4.4. Unlike the Level 3 IPs, Google openly acknowledges and documents these servers for public use.

Considerations and Cautions ⚠️

When using public DNS servers, it's crucial to do your research and ensure the servers are run by a reputable company. Hijacking outbound DNS requests with faulty responses can be an easy way to redirect users to malicious sites. It's generally recommended to use the name servers provided by your ISP outside of troubleshooting scenarios.

Public DNS servers often respond to ICMP echo requests, making them a great choice for testing general internet connectivity using the ping command. 🧭